Thiolate complexes of iridium. Structures of [Ir2(μ-SC6F5)2(cod)2], [Ir(SC6F5)(H)(SiPh3)(XNC)3] and [Ir3(μ-SC6F5)2</su

Article abstract of DOI:10.1016/j.poly.2008.03.001

The complex [Ir₂(μ-SC₆F₅)₂(cod)₂] (1) (cod = 1,5-cyclooctadiene), readily prepared in good yield from [Ir₂(μ-OMe)₂(cod)₂], combines with Ph₃SiH and XNC (XNC

Full text of DOI:10.1016/j.poly.2008.03.001

Polyhedron 27 (2008) 1959–1962
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Polyhedron
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Thiolate complexes of iridium. Structures of [Ir2(l-SC6F5)2(cod)2],
[Ir(SC6F5)(H)(SiPh3)(XNC)3] and [Ir3(l-SC6F5)2(SC6F5)(l,l0-XNC)(XNC)4(cod)]
(XNC = xylyl isocyanide)
*
Laurence Carlton , Zikhona N. Tetana, Manuel A. Fernandes
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050 Johannesburg, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history:
The complex [Ir2(l-SC6F5)2(cod)2] (1) (cod = 1,5-cyclooctadiene), readily prepared in good yield from
[Ir2(l-OMe)2(cod)2], combines with Ph3SiH and XNC (XNC = 2,6-dimethylphenylisocyanide, xylyl isocya-
nide) in benzene to give [Ir(SC6F5)(H)(SiPh3)-(XNC)3] (2). With XNC alone, in CH2Cl2, 1 reacts to give,
among other, unidentified products, [Ir3(l-SC6F5)2(SC6F5)(l,l0-XNC)(XNC)4(cod)] (3). The X-ray crystal
structures of 1, 2 and 3 are reported.
Received 26 November 2007
Accepted 5 March 2008
Available online 16 April 2008
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Iridium
Pentafluorophenylthiolate
Xylyl isocyanide
Trinuclear cluster
Crystal structure
1. Introduction
practicability of using xylyl isocyanide as a bridge-splitting reagent
is examined.
Complexes of rhodium and iridium containing thiolate ligands
are potentially valuable in homogeneous catalysis and related
chemistry [1–4], particularly chemistry involving bimetallic sys-
tems where the thiolate can serve as a bridging ligand. The penta-
fluorophenylthiolate ligand has a fairly high polarisability and can
be expected to offer enhanced reactivity (relative to that of the
chloro or N- or O-donor ligands) to a metal. The chemistry of
Rh(I) and Ir(I) with SC6F5 as the anionic ligand can conveniently
be studied by starting from an appropriate dinuclear complex such
as [(CO)2M(l-SC6F5)2M(CO)2] [5–8], [(1,5-cod)M((l-SC6F5)2M(1,5-
cod)] [8–10] and, for Rh(I), [(Ph3P)2Rh(l-SC6F5)2Rh(PPh3)2] [11]
and [(C2H4)2Rh((l-SC6F5)2Rh(C2H4)2] [5]. Our interest in SC6F5 as
a ligand for iridium arises from studies of the influence of ligand
polarisability on metal reactivity [12,13]. The use of 1,5-cycloocta-
diene as co-ligand extends work that demonstrates the activation
of Si–H bonds by [Ir(1,5-cod)(pyridine-2-carboxylate)] and related
compounds [14] and also circumvents difficulties that may arise as
a result of using triphenylphosphine (the complex [Ir(Cl)(PPh3)3]
undergoes intramolecular oxidative addition of C–H [15]). The
2. Experimental
2.1. Materials
[Ir2(l-OMe)2(cod)2] was prepared from chloroiridic acid using a
published method [16]. 1,5-Cyclooctadiene, C6F5SH and Ph3SiH
were purchased from Aldrich, xylyl isocyanide was purchased from
Fluka. CH2Cl2 was distilled from P2O5, benzene and hexane were
dried over CaH2. All operations were performed under an argon
atmosphere.
2.2. Preparation of [Ir2(l-SC6F5)2(cod)2] (1)
A stirred solution of [Ir2(l-OMe)2(cod)2] (0.137 g, 0.4 mmol,
based on Ir) in CH2Cl2 (2 ml) at room temperature was treated with
C6F5SH (eight drops, ꢀ0.4 mmol). A colour change from yellow to
dark red was immediately observed. After 20 min hexane was
added and the mixture was concentrated to give a yellow micro-
crystalline powder. The product was washed with hexane. Yield:
0.155 g (75%). 1H NMR (C6D6, 300 K) d 3.89 (S, broad, 4H), 2.03
(mult, broad, 4H) 1.44 (mult, 4H). Anal. Calc. for C28H24F10Ir2S2
C, 33.66; H, 2.42. Found: C, 33.80; H, 2.78%. Crystals suitable
* Corresponding author. Tel.: +27 11 7176727; fax: +27 11 7176749.
E-mail address: laurence.carlton@wits.ac.za (L. Carlton).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.03.001

1960
L. Carlton et al. / Polyhedron 27 (2008) 1959–1962
Table 1
Crystal data and structure refinement for 1, 2, and 3
[Ir2(l-SC6F5)2(cod)2] (1)
[Ir(SC6F5)(H)(SiPh3)(XNC)3](C6H6)
(2)
[Ir3(l-SC6F5)2(SC6F5)(ll0-XNC)(XNC)4(cod)]-
(n-hexane) (3)
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
b(Å)
c(Å)
a (°)
b (°)
C
28H24F10Ir2S2
C54H46F5IrN3SSi
1084.29
173(2)
0.71073
monoclinic
P21/n
C77H71F15Ir3N5S3
2024.17
173(2)
0.71073
monoclinic
P21/n
998.99
173(2)
0.71073
triclinic
ꢀ
P1
9.9103(2)
11.4053(2)
13.0978(2)
76.705(1)
79.999(1)
75.487(1)
1384.17(4)
2
2.397
1.001
R1 = 0.0265,
wR2 = 0.0603
2.523 and ꢁ1.375
11.6883(2)
24.0283(5)
16.9430(3)
90
98.102(1)
90
4710.95(15)
4
14.1753(2)
20.2895(3)
25.6554(4)
90
95.804(1)
90
7340.92(19)
4
c (°)
Volume (Å3)
Z
Dcalc (Mg/m3)
Goodness-of-fit on F2
R indices [I > 2r(I)]
1.529
0.978
1.831
1.055
R1 = 0.0341, wR2 = 0.0824
R1 = 0.0305, wR2 = 0.0642
Minimum and maximum residual densities
1.655 and ꢁ1.587
2.402 and ꢁ0.653
(e Åꢁ3
)
for X-ray diffraction were grown by evaporation of a chloroform
solution.
tures were solved by direct methods using SHELXTL [19]. Non-hydro-
gen atoms were first refined isotropically followed by anisotropic
refinement by full matrix least-squares calculations based on F2
using SHELXTL. With the exception of the hydride (structure 2) all
hydrogen atoms were first located in the difference map, then posi-
tioned geometrically and allowed to ride on their respective parent
atoms. The hydride of 2 was placed geometrically, equidistant from
the adjacent C, S and Si atoms and 1.60 Å from the iridium atom.
The structure of 2 contains disorder. One of the phenyl groups
of the triphenylsilane was found to be disordered and was refined
with isotropic atoms over three positions using rigid body re-
straints. Final occupancies were 0.36(1), 0.30(1) and 0.34(1) for
the three respective positions. One of the neighbouring isocyanide
ligands was also found to be disordered and was refined over two
positions using rigid body, SIMU, SADI and FLAT restraints with the
final occupancies being 0.48(1) and 0.52(1), respectively. The
structure also contains a benzene solvent molecule which was
found to be disordered over a centre of inversion. This was refined
isotropically as a rigid body with a site occupancy of 0.5. Crystal
and refinement data are given in Table 1.
2.3. Preparation of [Ir(SC6F5)(H)(SiPh3)(XNC)3](C6H6) (2)
A stirred mixture of [Ir2(l-SC6F5)2(cod)2] (0.015 g, 0.030 mmol)
and Ph3SiH (0.009 g, 0.035 mmol) in benzene (ꢀ1 ml) was treated
with xylyl isocyanide (0.012 g, 0.091 mmol) to give (within sec-
onds) a pale yellow solution. The solution was concentrated and
hexane was added. After 3 days at ꢁ20 °C colourless crystals were
obtained which were washed with hexane. Yield: 0.018 g (53%). 1H
NMR (C6D6, 300 K) d 7.90–6.57 (mults, aromatic H), 2.13 (S, 6H,
CH3), 2.10 (S, 12H, CH3), ꢁ8.55 (S, 1H, IrH). Elemental analysis
showed the percentage of carbon to be lower than that calculated
for 2, possibly as a result of loss of co-crystallised benzene.
2.4. Preparation of [Ir3(l-SC6F5)2(SC6F5)(l,l0-XNC)(XNC)4(cod)] (3)
A mixture of 1 (0.085 g, 0.017 mmol) and xylyl isocyanide
(0.0025 g, 0.019 mmol) was dissolved in CH2Cl2 (ꢀ1 ml) to give a
dark red solution. The solution was treated with hexane, concen-
trated and allowed to stand at ꢁ20 °C for 6 days to give an orange
powder (2.3 mg) and a few small orange crystals/crystalline lumps.
Yield of crystalline material ꢀ0.5 mg (ꢀ4% based on Ir). 1H NMR of
the powder indicated a mixture of products. Attempts to repeat the
result failed to yield crystals.
C22
C21
C17
C18
C15
C16
C19
Ir2
C20
2.5. NMR spectroscopy
1H spectra were recorded on a Bruker DRX 400 spectrometer
and referenced to TMS (internal standard).
S2
C9
2.6. X-ray structure determination
S1
C23
Ir1
C8
C6
Intensity data were collected on a Bruker APEX II CCD area
detector diffractometer with graphite monochromated Mo Ka radi-
ation (50 kV, 30 mA) using the APEX2 [17] data collection software.
The collection method involved x-scans of width 0.5° and
512 ꢂ 512 bit data frames. Data reduction was carried out using
the program SAINT+ [18]. Face indexed absorption corrections were
carried out for 1 and 2 using XPREP [18] while multiscan absorption
corrections were carried out for 3 using SADABS. The crystal struc-
C1
C2
C7
C5
C4
C3
Fig. 1. Thermal ellipsoid plot of [Ir2(l-SC6F5)2(cod)2] (1) with ellipsoids drawn at
the 30% probability level.

L. Carlton et al. / Polyhedron 27 (2008) 1959–1962
1961
Table 2
Selected bond lengths (Å) and angles (°)
(a) [Ir2(l-SC6F5)2(cod)2] (1)
Bond lengths
Ir(1)–C(1)
Ir(1)–C(2)
Ir(1)–C(5)
Ir(1)–C(6)
Ir(1)–S(1)
2.124(4)
Ir(1)–S(2)
2.3466(10)
2.125(4)
2.130(4)
2.129(4)
2.123(4)
Ir(2)–S(1)
Ir(2)–S(2)
S(1)–C(9)
S(2)–C(23)
2.3622(10)
2.3598(9)
1.771(4)
2.140(4)
2.116(4)
2.143(4)
2.3629(9)
Ir(2)–C(15)
Ir(2)–C(16)
Ir(2)–C(19)
Ir(2)–C(20)
1.765(4)
Bond angles
S(1)–Ir(1)–C(1)
S(1)–Ir(1)–C(2)
S(1)–Ir(1)–C(5)
S(1)–Ir(1)–C(6)
S(1)–Ir(1)–S(2)
S(1)–Ir(2)–S(2)
160.17(13)
159.94(12)
94.95(11)
98.85(11)
76.38(3)
S(2)–Ir(1)–C(1)
S(2)–Ir(1)–C(2)
S(2)–Ir(1)–C(5)
S(2)–Ir(1)–C(6)
Ir(1)–S(1)–Ir(2)
Ir(1)–S(2)–Ir(2)
99.82(12)
97.63(11)
150.10(12)
169.25(12)
93.62(3)
Ir(1)–S(1)–C(9)
Ir(1)–S(2)–C(23)
Ir(2)–S(1)–C(9)
Ir(2)–S(2)–C(23)
112.59(13)
116.36(13)
114.51(14)
117.16(13)
76.14(3)
94.10(3)
(b) [Ir(SC6F5)(H)(SiPh3)(XNC)3](C6H6) (2)
Bond lengths
Ir–S
Ir–Si
2.4919(10)
2.3963(10)
Ir–C(21)
Ir–C(31)
1.941(3)
1.994(4)
Ir–C(41)
1.972(4)
Bond angles
S–Ir–Si
S–Ir–C(21)
S–Ir–C(31)
S–Ir–C(41)
172.91(4)
Si–Ir–C(21)
Si–Ir–C(31)
Si–Ir–C(41)
C(21)–Ir–C(31)
87.83(9)
92.22(10)
91.73(9)
98.87(14)
C(21)–Ir–C(41)
C(31)–Ir–C(41)
168.15(15)
92.98(14)
90.05(9)
94.80(10)
88.95(9)
(c) [Ir3(l-SC6F5)2(SC6F5)(ll0-XNC)(XNC)4(cod)](n-hexane) (3)
Bond lengths
Ir(1)–C(1)
Ir(1)–C(2)
Ir(1)–C(5)
Ir(1)–C(6)
Ir(1)–C(61)
Ir(1)–S(2)
2.203(5)
2.201(5)
2.146(5)
2.148(5)
2.011(5)
2.4698(13)
Ir(1)–S(3)
Ir(2)–C(41)
Ir(2)–C(51)
Ir(2)–C(61)
Ir(2)–S(1)
Ir(2)–S(2)
2.4624(13)
1.928(5)
1.920(6)
1.990(5)
2.4726(13)
2.3852(13)
Ir(3)–C(71)
Ir(3)–C(81)
Ir(3)–N(60)
Ir(3)–S(3)
C(61)–N(60)
Ir(1)–Ir(2)
1.879(5)
1.872(6)
2.112(4)
2.3716(13)
1.281(6)
2.6882(3)
Bond angles
Ir(1)–C(61)–Ir(2)
Ir(1)–S(2)–Ir(2)
Ir(1)–S(3)–Ir(3)
S(1)–Ir(2)–S(2)
S(1)–Ir(2)–C(41)
S(1)–Ir(2)–C(51)
S(1)–Ir(2)–C(61)
S(2)–Ir(1)–S(3)
S(2)–Ir(1)–C(61)
84.41(18)
67.22(3)
103.97(5)
95.53(4)
87.54(15)
101.53(15)
150.42(14)
87.32(4)
S(2)–Ir(2)–C(41)
S(2)–Ir(2)–C(51)
S(2)–Ir(2)–C(61)
S(3)–Ir(1)–C(61)
S(3)–Ir(3)–C(71)
S(3)–Ir(3)–C(81)
N(60)–Ir(3)–S(3)
N(60)–Ir(3)–C(71)
N(60)–Ir(3)–C(81)
168.80(15)
95.22(15)
76.27(14)
78.73(14)
170.83(16)
96.58(16)
81.64(11)
91.16(18)
178.04(19)
C(41)–Ir(2)–C(51)
C(41)–Ir(2)–C(61)
C(51)–Ir(2)–C(61)
C(61)–N(60)–C(62)
C(71)–Ir(3)–C(81)
Ir(3)–N(60)–C(61)
Ir(3)–N(60)–C(62)
94.7(2)
95.80(19)
107.4(2)
117.7(4)
90.7(2)
122.0(3)
120.0(3)
73.93(14)
When complex 1 in dichloromethane is treated with one equiv-
alent of XNC an immediate colour change from red to orange is ob-
served. Attempts to isolate a product yielded small quantities of 3
(Scheme 1 and Fig. 3), a trinuclear complex containing two bridg-
ing thiolates and a triply bridging isocyanide. Complex 3 exists in
two mirror image forms related, in the unit cell, by an inversion
centre. Selected bond lengths and angles are given in Table 2.
The N(60)–C(61) distance of 1.28 Å indicates a double bond consis-
3. Results and discussion
The complex [Ir2(l-SC6F5)2(cod)2] (1) was reported a number of
years ago by Terreros and co-workers [8] who prepared it from
[Ir2(l-Cl)2(cod)2] using a mixture of C6F5SH and NEt3. Our method,
starting from [Ir2(l-OMe)2(cod)2], offers a slightly improved yield
(75%). The structure of 1 (Fig. 1) has a geometry at Ir that can be
described as square planar distorted towards square pyramidal,
with the alkene groups each occupying a single coordination site.
Selected bond lengths and angles are given in Table 2. The sharply
angled Ir–S–Ir bonds cause the molecule to adopt a pyramidal
structure with the dienes and C6F5 groups forming the base and
the two sulphurs a truncated apex. Although the two iridiums bear
identical substituents and bridging groups which closely approach
a symmetrical arrangement, they are not related by any crystallo-
graphic symmetry element.
In dichloromethane at room temperature 1 is unreactive to-
wards triphenylsilane, but upon addition of xylyl isocyanide
(XNC) a product [Ir(SC6F5)(H)(SiPh3)(XNC)3] (2) is rapidly formed
regardless of whether one or three equivalents of XNC is used
(Scheme 1). The geometry of 2 (Fig. 2) is distorted octahedral, with
ligands showing displacement towards the hydride. The hydride
(the presence of which was confirmed by a 1H NMR signal at d
ꢁ8.55 ppm) was not located in the electron density map but in-
stead geometrically inserted. One of the phenyl groups of the silane
is disordered and was refined over three positions.
X
N
C
Ph3Si
CNX
Ph3SiH
XNC C6H6
(53%)
(~4%)
Ir
2
3
SC6F5
H
C
N
X
C6F5
S
Ir
S
Ir
C6F5
S
C6F5
SC6H5
XNC
CH2Cl2
Ir
Ir
Ir CNX
CNX
1
C
N
C6F5S
XNC
X
CNX
X = xylyl
Scheme 1.

1962
L. Carlton et al. / Polyhedron 27 (2008) 1959–1962
three iridiums are nominally in the +1 oxidation state. Dinuclear
iridium complexes having bridging (via carbon) isocyanides are
known [20,21] as are trinuclear rhodium [22] and osmium [23–
27] complexes having triply bridging isocyanides, bonded in the
manner of complex 3. To our knowledge 3 is the first example of
an iridium complex exhibiting such bonding. Whilst it is possible
to speculate that the initial stages of formation of 3 might involve
nucleophilic attack of an electron-rich derivative of 1, possibly
[Ir(SC6F5)(XNC)(cod)], on the a carbon of a coordinated isocyanide,
further work is required to establish the identity of this reactive
intermediate.
S
C41
N40
N30
Ir
C31
H
C21
N20
4. Supplementary data
CCDC 668581, 668582 and 668583 contain the supplementary
crystallographic data for 1, 2 and 3. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Si
Fig. 2. Thermal ellipsoid plot of [Ir(SC6F5)(H)(SiPh3)(XNC)3] (2) with ellipsoids
drawn at the 30% probability level. A co-crystallised benzene is omitted. Hydride
inserted geometrically.
Acknowledgement
We thank the University of the Witwatersrand for financial
support.
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Fig. 3. Thermal ellipsoid plot of [Ir3(l-SC6F5)2(SC6F5)(ll0-XNC)(XNC)4(cod)] (3) with
ellipsoids drawn at the 30% probability level. A co-crystallised n-hexane is omitted.
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tent with an imino group, i.e. the bridging isocyanide might more
accurately be regarded as an iminocarbene. In this formulation a
lone pair of electrons becomes available on the nitrogen to partake
in further bonding to give a triply bridged structure in which all