Intramolecular dehydrofluorinative coupling of pentamethylcyclopentadienyl and phosphine ligands in iridium complexes

Article abstract of DOI:10.1016/j.poly.2004.05.014

Cationic iridium(III) complexes of bifunctional η⁵,κP- Cp-P and trifunctional η⁵,κP,κL-Cp-PL ligands may be conveniently prepared by intramolecular dehydrofluorinative carbon-carbon coupling. The iridium(III) complex [(η⁵-C₅Me ₅)IrCl(dfppe)]BF₄ (dfppe=(C₆F₅) ₂PCH₂CH₂P(C₆F₅) ₂) undergoes rapid dehydrofluorinative coupling on addition of proton sponge to produce [{η⁵,κP,κP-C₅Me ₃[CH₂C₆F₄-2-P(C₆F ₅)CH₂]₂-1,3}IrCl]BF₄. The reaction requires less than the stoichiometric quantity of proton sponge and also occurs on addition of Buⁿ₄NF. The cationic phosphine-thioether complex [(η⁵-C₅Me₅)IrCl{κP,κS- (C₆F₅)₂PC₆H₄SMe-2}] BF₄ undergoes rapid dehydrofluorinative coupling to [{η⁵,κP,κS-C₅Me₄CH ₂C₆F₄-2-P(C₆F₅)C ₆H₄SMe-2}IrCl]BF₄ on treatment with proton sponge. NMR studies indicate that on treatment with proton sponge the cations [(η⁵-C₅Me₅)IrCl(CNR){PPh₂(C ₆F₅)}]⁺ (R=Ph or ^tBu) undergo coupling to give [(η⁵,κP-C₅Me₄CH ₂C₆F₄-2-PPh₂)IrCl(CNR)] ⁺, but at a much slower rate and less cleanly than for the cations containing chelating ligands. The neutral compound [(η⁵-C ₅Me₅)IrCl₂{PPh₂(C₆F ₅)}] does not undergo coupling, indicating that a positive charge is necessary for the reaction. The results are analogous to those for rhodium complexes.

Full text of DOI:10.1016/j.poly.2004.05.014

Polyhedron 23 (2004) 2659–2664
www.elsevier.com/locate/poly
Intramolecular dehydrofluorinative coupling of
pentamethylcyclopentadienyl and phosphine ligands in
iridium complexes
*
Ronan M. Bellabarba, Graham C. Saunders
School of Chemistry, Queen’s University Belfast, David Keir Building, Belfast BT9 5AG, UK
Received 13 April 2004; accepted 20 May 2004
Available online 15 July 2004
Dedicated to Prof. Malcolm Green FRS for his guidance and inspiration
Abstract
Cationic iridium(III) complexes of bifunctional g5,jP-Cp–P and trifunctional g5,jP,jL-Cp–PL ligands may be conveniently
prepared by intramolecular dehydrofluorinative carbon–carbon coupling. The iridium(III) complex [(g5-C5Me5)IrCl(dfppe)]BF4
(dfppe ¼ (C6F5)2PCH2CH2P(C6F5)2) undergoes rapid dehydrofluorinative coupling on addition of proton sponge to produce
[{g5,jP,jP-C5Me3[CH2C6F4-2-P(C6F5)CH2]2-1,3}IrCl]BF4. The reaction requires less than the stoichiometric quantity of proton
sponge and also occurs on addition of Bun4NF. The cationic phosphine–thioether complex [(g5-C5Me5)IrCl{jP,jS-
(C6F5)2PC6H4SMe-2}]BF4 undergoes rapid dehydrofluorinative coupling to [{g5,jP,jS-C5Me4CH2C6F4-2-P(C6F5)C6H4SMe-
2}IrCl]BF4 on treatment with proton sponge. NMR studies indicate that on treatment with proton sponge the cations
t
[(g5-C5Me5)IrCl(CNR){PPh2(C6F5)}]þ (R ¼ Ph or Bu) undergo coupling to give [(g5,jP-C5Me4CH2C6F4-2-PPh2)IrCl(CNR)]þ,
but at a much slower rate and less cleanly than for the cations containing chelating ligands. The neutral compound [(g5-
C5Me5)IrCl2{PPh2(C6F5)}] does not undergo coupling, indicating that a positive charge is necessary for the reaction. The results are
analogous to those for rhodium complexes.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
less a number of rhodium complexes of Cp–P and Cp–PL
ligands have been reported [4–6,9,11–14]. In contrast the
number of complexes of iridium is limited to those of the
Cp–P ligands 1 [15,16] and 2 [17], and 3 [18].
Transition metal complexes of chelating bifunc-
tional g5,jP-cyclopentadienyl–phosphine (Cp–P) or tri-
functional g5,jP,jL-cyclopentadienyl–phosphine-donor
(Cp–PL) ligands can possess benefits over the analogous
complexes of the unlinked ligands. Enhancement of
stability [1–4], reactivity [5,6] and regio and stereo-se-
lectivity in their reactions [7] has been reported, and
configurational stability is expected for chiral-at-metal
complexes of Cp–PL ligands [8]. Despite the benefits
relatively few complexes of Cp–P ligands, and even fewer
of Cp–PL ligands, have been reported, primarily due to
the lack of convenient synthetic routes [9,10]. Nonethe-
R
R'
-
BF4
3
-
PMe2
PPh2
2
1
R = H, R' = H or cyclo-C6H11
R = Ph, R' = H
F
F
Cl
Ir
F
F
* Corresponding author. Tel.: +44-28-90374682; fax: +44-28-
90382117/+44-28-90273333.
E-mail address: g.saunders@qub.ac.uk (G.C. Saunders).
P
P
F
F
C6F5
C6F5
F
F
0277-5387/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.05.014

2660
R.M. Bellabarba, G.C. Saunders / Polyhedron 23 (2004) 2659–2664
We have demonstrated that intramolecular dehydro-
2. Experimental
fluorinative carbon–carbon coupling provides a conve-
nient route to cationic rhodium complexes of Cp–P and
Cp–PL ligands [12]. The coupling of the pentamethylcy-
clopentadienyl and fluorophenylphoshphines of cationic
complexes of the formula [(g5-C5Me5) RhXL{PR2
(C6F5)}]þ (X ¼ Cl or Br, L ¼ 2-electron donor ligand)
may be performed by addition of less than one equivalent
of 1,8-bis(dimethylamino)naphthalene (proton sponge)
or fluoride ions. The reaction is rapid and quantitative for
complexes in which the phosphine is part of a chelating
ligand, as in a diphosphine or a phosphine-thioether, but
considerably slower for complexes of monodentate
phosphines. Alternatively, for cations containing chelat-
ing phosphines, heating a solution of the salt in an ap-
propriate solvent yields the coupled product, although
not always cleanly [18,19]. The preparation of the com-
plexes of trifunctional cyclopentadienyl–diphosphine li-
gands containing two linkages has also been
accomplished by heating a slurry of a 2:1 mixture of the
diphosphine and [(g5-C5Me5)RhCl(l-Cl)]2 in benzene or
ethanol [18,20]. The last method has also been found to
yield 3 from [(g5-C5Me5)IrCl(l-Cl)]2 and (C6F5)2PCH2
CH2P(C6F5)2 (dfppe) [18]. A mechanism involving for-
mation of an g4-fulvene by loss of a proton from the
pentamethylcyclopentadienyl ligand and intramolecular
nucleophilic attack of the methylene carbon on an ortho
C–F bond has been proposed for cationic rhodium(III)
and cobalt(III) complexes [12,21]. The similarity of the
chemistry of analogous rhodium(III) and iridium(III)
pentamethylcyclopentadienyl complexes suggests that
intramolecular dehydrofluorinative carbon–carbon cou-
pling would also provide a convenient route to Cp–P and
Cp–PL complexes of iridium. In support g4-fulvene
complexes of iridium have been proposed as nucleophilic
intermediates in a number of reactions [22–26] and [(g4-
C5Me4CH2)IrMe(dppe)] has been structurally charac-
terized [27]. However, some differences in reactivity
between analogous complexes of iridium and rhodium
have been observed. One apposite example is provided
by the reactions between [(g5-C5Me5)MCl(l-Cl)]2 and
(C6H3 F2-2,6)2PCH2CH2P(C6H3F2-2,6), which yielded
the coupled product 4 and the uncoupled bimetallic
compound 5 [19]. Therefore, we set out to examine
whether the coupling reactions that occur for the cationic
rhodium complexes also occur for the analogous comp-
lexes of iridium. Here, the results of our study are reported.
2.1. Physical measurements
The 1H, 19F and 31P NMR spectra were recorded
using a Bruker DPX300 spectrometer. 1H (300.01 MHz)
were referenced internally using the residual protio sol-
vent resonance relative to SiMe4 (d 0), 19F (282.26 MHz)
externally to CFCl3 (d 0) and 31P (121.45 MHz) exter-
nally to 85% H3PO4 (d 0). All spectra were recorded in
CDCl3 at 300 K. Data are given as chemical shifts (d)
using the high frequency positive convention, [relative
intensity, multiplicity, J/Hz, assignment], s, singlet; d,
doublet; t, triplet; m, multiplet; br, broad. The IR
spectra were recorded on a Perkin–Elmer RX I Fourier
transform spectrometer. Mass spectra were recorded on
a VG Autospec X series mass spectrometer. Elemental
analyses were carried out by A.S.E.P., The School of
Chemistry, Queen’s University Belfast.
2.2. Materials
The compounds [(g5-C5Me5)IrCl(l-Cl)]2, sodium
tetrafluoroborate and proton sponge (Aldrich) were
used as supplied. The salt [(g5-C5Me5)IrCl(dfppe)]BF4
[18] and phenylisonitrile [28] were prepared as described.
The phosphines P(C6F5)3 and PPh2(C6F5) [29] were
prepared from PCl3 and Ph2PCl as described for similar
compounds [30].
2.3. (C6F5)2PC6H4SMe-2 (6)
A solution of BunLi in hexane (3.0 cm3, 1.6 M) was
added to MeSC6H4Br-2 (1.10 g, 5.4 mmol) in diethyl
ether at 0 °C. After stirring for 1 h the solution was
added over 10 min to P(C6F5)3 (3.12 g, 5.8 mmol) in
diethyl ether (100 cm3) at 0 °C to give a black solution.
After stirring for a further 5 min water (100 cm3) was
added. The organic layer was washed with water (100
cm3). The aqueous layer and washings were extracted
with 1:2 ethyl acetate/chloroform (200 cm3). The com-
bined organic extracts were dried over magnesium sul-
fate. Filtration and removal of the solvent by rotary
evaporation yielded a brown oil comprising P(C6F5)3,
(6) and (C6F5)P(C6H4SMe-2)2. Compound 6 was ob-
tained by distillation by kugelrohr at 130–140 °C and
0.03 mm Hg. Yield 0.120 g (4.2%).
2.4. [(g5-C5Me5)IrCl{jP, jS-(C6F5)2PC6H4SMe-2}]-
BF4 (7)
BF4
Ir
Cl
Cl
Cl
Cl
Ar2P
Cl Rh
P
Sodium tetrafluoroborate (0.164 g, 1.5 mmol) was
added to [(g5-C5Me5)IrCl(l-Cl)]2 (0.175 g, 0.22 mmol)
and 6 (0.216 g, 0.44 mmol) in dichloromethane (30 cm3)
and methanol (30 cm3), and the mixture stirred for 90
min. The solvent was removed by rotary evaporation
PAr2
Ir
P
F
F
Ar
Ar
4
5
Ar = C6H3F2-2,6

R.M. Bellabarba, G.C. Saunders / Polyhedron 23 (2004) 2659–2664
2661
and the product extracted into dichloromethane. The
extract was filtered and the solvent removed by rotary
evaporation to give the product as a yellow solid. Yield
0.351 g (87%). Anal. Calc. for C29H22BClF14PIrS (7): C,
2.7. [(g5-C5Me5)IrCl(CNPh){PPh2(C6F5)}]BF4 (10a)
Sodium tetrafluoroborate (0.110 g, 1.00 mmol) in
methanol (30 cm3) was added to 9 (0.100 g, 0.13 mmol)
and phenylisonitrile (0.108 g, 1.05 mmol) in dichlo-
romethane/methanol (30 cm3), and the mixture stirred
for 2 h. The solvent was removed by rotary evaporation
and the product extracted into dichloromethane. Con-
centration by rotary evaporation and addition of hexane
precipitated the product as a yellow solid. Yield 0.070 g
(59.1%). Anal. Calc. for C35H30BClF9IrNP.0.5CH2Cl2
(10a): C, 44.7; H, 3.9; N, 1.5. Found: C, 45.15; H, 3.15;
N, 1.75%. m(NBC) 2181 cmꢀ1. 1H NMR: d 7.85 (2H, m),
7.33 – 7.54 (11H, m), 6.86 (2H, m), 5.30 (1H, s, CH2Cl2),
1.80 [15H, d, 4J(PH) 2.7, Me]. 19F NMR: d )124.67 (2F,
m, Fo), )143.55 (1H, br s, Fp), )153.68 (0.8F, s, 10BF4ꢀ),
)153.74 (3.2F, s, 11BF4ꢀ), )156.93 (2F, br s, Fm).
31P{1H} NMR: d 9.4 (s).
1
37.0; H, 2.4. Found: C, 36.9; H, 2.2%. H NMR: d 8.55
(1H, m, C6H4), 8.10 (2H, m, C6H4), 7.98 (1H, m, C6H4),
3.14 (3H, s, SMe), 1.78 (15H, s, Me). 19F NMR: )122.50
(1F, br s, Fo), )127.32 (1F, br s, Fo), )127.55 (1F, br s,
Fo), )131.76 (1F, br s, Fo), )141.99 (1F, br s, Fp),
)144.65 (1F, br s, Fp), )153.59 (0.8F, s, 10BF4ꢀ), )153.64
(3.2F, s, 11BF4ꢀ), )155.14 (1F, br s, Fm), )157.24 (1F, br
s, Fm), )158.41 (1F, br s, Fm), )160.61 (1F, br s, Fm).
31P{1H} NMR: 5.4 (s).
2.5. [{g5,jP,jS-C5Me4CH2C6F4-2-P(C6F5)C6H4SMe-
2}IrCl]BF4 (8)
Proton sponge (0.041 g, 0.19 mmol) was added to 7
(0.129 g, 0.14 mmol) in dichloromethane (40 cm3) and
the solution left at ambient temperature for 48 h. The
solution was washed with water (50 cm3), dilute hy-
drochloric acid (50 cm3) and water (50 cm3), and dried
over magnesium sulfate. Filtration and removal of the
solvent by rotary evaporation gave the product as a
yellow solid, which was dried in vacuo. Yield 0.084 g
(66.5%). Anal. Calc. for C29H21BClF13PIrS (8): C, 37.9;
H, 2.3. Found: C, 40.05; H, 2.6%. Repeated washing
and drying in vacuo failed to give satisfactory analysis
(N < 0:1%). LSIMS: 831 ([M ) BF4]þ) [Found:
831.02980 C29H21ClF9193IrPS requires 831.02759]. 1H
NMR: d 8.14 (1H, m, C6H4), 7.97 (1H, m, C6H4), 7.74
(1H, m, C6H4), 7.66 (1H, m, C6H4), 4.58 [1H, dd,
2J(HH) 17.9, 4J(PH) 7.6, CH2], 3.05 [1H, d, 2J(HH)
2.8. [(g5-C5Me5)IrCl(CNBut){PPh2(C6F5)}]BF4 (10b)
t
Compound 9 (0.060 g, 0.08 mmol), butylisonitrile
(0.009 cm3, 0.08 mmol) and sodium tetrafluoroborate
(0.109 g, 1.00 mmol) were treated as for 10a. Yield 0.045
g (63.6%). Anal. Calc. for C33H34BClF9IrNP (10b): C,
44.8; H, 3.9; N, 1.6. Found: C, 44.5; H, 3.9; N, 1.75%.
LSIMS: 798 ([M ) BF4]þ), 763 ([M ) BF4 ) Cl]þ)
[Found: 798.16367 C33H34BClF1993IrNP requires
1
798.16670]. m(NBC) 2199 cmꢀ1. H NMR: d 7.79 (2H,
4
m), 7.37 )7.63 (8H, m), 1.72 [15H, d, J(PH) 2.6, Me],
t
1.29 (9H, s, Bu). 19F NMR: d )124.71 (2F, m, Fo),
)144.04 (1H, br s, Fp), )153.87 (0.8F, s, 10BF4ꢀ),
)153.96 (3.2F, s, 11BF4ꢀ), )157.22 (2F, br s, Fm).
31P{1H} NMR: d )9.0 (s).
4
17.9, CH2], 2.65 (3H, s, SMe), 2.34 [3H, d, J(PH) 6.5,
CH3], 1.87 [3H, d, 4J(PH) 2.2, CH3], 1.82 [3H, d, 4J(PH)
2.9, CH3], 1.69 (3H, s, CH3). 19F NMR: d )119.47 (1F,
m), )128.81 (1F, m), )133.22 (1F, m), )133.52 (1F, m),
)142.81 (1F, m), )146.05 [1F, t 3J(FF) 20.7], 151.97 [1F,
2.9. [(g5,jP-C5Me4CH2C6F4-2-PPh2)IrCl(CNPh)]BF4
(11a)
t
3J(FF) 22.0, Fp], )153.77 (0.8F, s, 10BFꢀ4 ), )153.83
Proton sponge (0.005 g, 0.023 mmol) was added to
10a (0.057 g, 0.063 mmol) in dichloromethane (15
cm3). After 7 days dichloromethane (85 cm3) was ad-
ded and the solution washed with water (3 ꢁ 50 cm3)
and dried over magnesium sulfate. Filtration and re-
moval of the solvent by rotary evaporation gave an
oily brown solid, which was washed with diethyl ether
(10 cm3) and dried in vacuo. Yield 0.045 g (80.7%).
Anal. Calc. for C35H29BClF8IrNP (11a): C, 47.5; H,
3.3; N, 1.6. Found: C, 49.4; H, 3.9; N, 1.9%. Repeated
washing and drying in vacuo failed to give satisfactory
analysis. LSIMS: 798 ([M ) BF4]þ), 763 ([M ) BF4 )
Cl]þ) [Found: 798.12522 C35H29ClF1493 IrNP requires
(3.2F, s, 11BF4ꢀ), )158.85 (2H, m). 31P{1H} NMR: d
31.9 (s).
2.6. [(g5-C5Me5)IrCl2{PPh2(C6F5)}] (9)
A mixture of [(g5-C5Me5)IrCl(l-Cl)]2 (0.112 g, 0.14
mmol) and Ph2P(C6F5) (0.099 g, 0.28 mmol) in dichlo-
romethane/methanol (50 cm3) was left at ambient tem-
perature for 2 h. The solvent was removed by rotary
evaporation affording the product as an orange solid,
which was recrystallized from dichloromethane. Yield
0.160 g (76.1%). Anal. Calc. for C28H27Cl2F5PIr (9): C,
44.8; H, 3.4. Found: C, 44.5; H, 3.1%. H NMR: d 7.81
798.12917]. m(NBC) 2180 cmꢀ1. H NMR: d 7.05–7.82
1
1
(4H, m, C6H5), 7.41 (6H, m, C6H5), 1.44 [15H, d,
4J(PH) 2.5, Me]. 19F NMR: d )120.06 (2F, m, Fo),
)148.52 [1F, t, 3J(FmFp) 19.8, Fp], )160.22 (2F, m, Fm).
31P{1H} NMR: )1.7 (s).
(15H, m, C6H5), 3.85 [1H, dd, 2J(HH) 16.9, 4J(PH)
4.8, CH2], 3.64 [1H, dd, 2J(HH) 16.9, 4J(PH) 4.8,
CH2], 2.30 [3H, d, 4J(PH) 4.0, CH3], 1.90 [3H, d,
4
4J(PH) 4.3, CH3], 1.73 [3H, d, J(PH) 4.4, CH3], 1.51

2662
R.M. Bellabarba, G.C. Saunders / Polyhedron 23 (2004) 2659–2664
(3H, s, CH3). 19F NMR: d )118.64 (1F, m), )136.29
(1F, m), )145.78 (1F, m), )152.30 (1F, m), )153.05
(0.8F, s, 10BFꢀ4 ), )153.11 (3.2F, s, 11BFꢀ4 ). 31P{1H}
NMR: d 5.6 (s).
P(C6F5)3. Addition of one equivalent of MeSC6H4Li-2
to P(C6F5)3 in diethyl ether at 0 °C gave a black solu-
tion, consistent with the formation of C6F5Li. Follow-
ing hydrolysis a brown oil was isolated which was shown
by NMR spectroscopy to contain P(C6F5)3, (6) and
(C6F5)P(C6H4SMe-2)2 in roughly equal amounts. Al-
though the result confirms that the P–C6F5 bond can be
readily cleaved by organolithium reagents, the reaction
is not selective. Further, separating these phosphines
proved difficult, although slightly impure 6 was obtained
in ca. 4% yield by distillation by kugelrohr at 130–140
°C and 0.03 mm Hg. Thus this method of preparing 6 is
inferior to that we have reported previously [12].
2.10. [(g5,jP-C5Me4CH2C6F4-2-PPh2)IrCl(CNBut)]BF4
(11b)
A sample was obtained from the reaction between
10b and proton sponge in an NMR tube. There was
insufficient sample for elemental analysis. LSIMS: 778
([M ) BF4]þ), 743 ([M ) BF4 ) Cl]þ) [Found: 778.16394
C33H33ClF1493IrNP requires 778.160471]. m(NBC) 2197
cmꢀ1
.
19F NMR: d )120.71 (1F, m), )136.76 (1F, m),
Treatment of [(g5-C5Me5)IrCl(l-Cl)]2 with 6 in the
presence of an excess of sodium tetrafluoroborate
yielded the salt [(g5-C5Me5)IrCl{jP,jS-(C6F5)2PC6
)146.35 (1F, m), )152.45 (1F, m), )153.20 (0.8F, s,
10BFꢀ4 ), 153.25 (3.2F, s, 11BFꢀ4 ). 31P{1H} NMR: d 5.1
(s). Important 1H NMR resonances are given in Section
3 (vide infra).
1
H4SMe-2}]BF4, 7. The H and 19F NMR spectra of 7
are similar to those of the rhodium analogue [11,12].
The 19F NMR spectrum exhibits 10 resonances in
addition to those of tetrafluoroborate. Each fluorine
atom of the cation is unique due to hindered rotation
about the P–C6F5 bonds. The 31P{1H} spectrum ex-
hibits a singlet at d 5.4, which is to a lower frequency
of the doublet resonance of the rhodium analogue (d
30.2). This difference is consistent with differences ob-
served between rhodium and iridium analogues of
similar compounds [18,20]. There are two stereogenic
centres in the cation: the iridium and sulfur atoms.
However only one set of resonances is seen in the
NMR spectra, in particular there is only one thiom-
ethyl hydrogen resonance, at d 3.14, strongly suggest-
ing that only one pair of enantiomers are present in
solution. It is expected that the RIrRS and SIrSS pair,
in which the methyl group is trans to the pentameth-
ylcyclopentadienyl ligand would be the thermody-
namically and kinetically preferred products for steric
reasons. It is not known whether the exclusive exis-
tence of one pair of enantiomers is as a result of ki-
netics of coordination of the thioether or whether the
other stereoisomers are formed and isomerize rapidly.
This process can occur by dissociation and re-coordi-
nation of the labile thioether or by inversion at coor-
dinated sulfur, which is presumed to have a low
activation barrier. In support of the latter, the pyra-
midal inversion at the sulfur of PPh(C6H4SMe-2)2,
jP,jS-coordinated to palladium, has a free energy of
activation, DGz, of 40–60 kJ molꢀ1 [32].
3. Results and discussion
An in situ NMR experiment in CDCl3 revealed that
the salt [(g5C5Me5)IrCl(dfppe)]BF4 underwent rapid
intramolecular dehydrofluorinative carbon–carbon
coupling in the presence of less than one equivalent of
proton sponge to give 3 [18]. As for the rhodium ana-
logue, the fluoride generated as the by-product acted as
a base. An in situ NMR experiment confirmed that the
coupling occurred rapidly on addition of tetrabutylam-
monium fluoride to [(g5-C5Me5)IrCl(dfppe)]BF4 in
acetone. In contrast [(g5-C5Me5)IrCl{jP,jP-[(C6H3F2-
2,6)2PCH2]2}]BF4 [20] did not undergo any reaction in
the presence of proton sponge in CDCl3 at ambient
temperature over 24 h. This observation is consistent
with the lack of a coupling reaction of this salt in re-
fluxing ethanol and also when [(g5-C5Me5)IrCl(l-Cl)]2
and (C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6) are heated
in benzene. The rhodium analogue [(g5-C5Me5)
RhCl{jP,jP-[(C6H3F2-2,6)2PCH2]2}]BF4 also did not
undergo a reaction with proton sponge. This salt also
underwent no reaction in refluxing ethanol, but dehy-
drofluorinative carbon–carbon coupling was observed in
the reaction between [(g5-C5Me5)RhCl(l-Cl)]2 and
(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6) in benzene [20].
We wished to attempt the coupling reaction with an
iridium complex of the phosphine-thioether (C6F5)2
PC6H4SMe-2, (6), which possesses only one phosphine
functionality. Compound 6 has been prepared by the
reaction between MeSC6H4Li and (C6F5)2PBr [12], but
following the observation that when a mixture of
(C6F5)PPhCl and (C6F5)PPhBr was treated with an
excess of MeSC6H4Li-2 the phosphine PhP(C6H4
SMe2)2 was formed, consistent with previous reports of
P–C6F5 bond cleavage by Grignard reagents [31], it was
decided to investigate whether 6 could be prepared from
An in situ NMR spectroscopic study revealed that on
treatment with proton sponge 7 underwent rapid intra-
molecular dehydrofluorinative coupling to give salt 8
(Scheme 1), which was isolated in 67% yield from a
1
preparative scale reaction. The H and 19F NMR spec-
tra of 8 are similar to those of the rhodium analogue
[11,12] and the 31P{1H} spectrum exhibits a singlet at d
31.9. The shift of the phosphorus resonance to higher
frequency on coupling of the phosphine to the pen-

R.M. Bellabarba, G.C. Saunders / Polyhedron 23 (2004) 2659–2664
2663
Treatment of [(g5-C5Me5)IrCl(l-Cl)]2 with PPh2
(C6F5) yielded the neutral complex [(g5-C5Me5)IrCl2
{PPh2(C6F5)}] (9). Consistent with the rhodium ana-
logue, compound 9 underwent no reaction with proton
sponge. The cationic iridium complexes [(g5-
C5Me5)IrCl(CNR){PPh2(C6F5)}]BF4 (10a R ¼ phenyl;
10b R ¼ t-butyl) were prepared by treatment of 9 with
the appropriate isonitrile in the presence of an excess of
BF4
BF4
F
proton sponge,
CH2Cl2
Ir
Ir
Cl
Cl
S
S
F
(C6F5)2P
P
F
7
F
8
C6F5
Scheme 1.
1
sodium tetrafluoroborate (Scheme 2). The H and 19F
tamethylcyclopentadienyl ligand is consistent with pre-
vious observations [12,18,20]. The 1H spectroscopic
studies show NOE correlation between the thiomethyl
hydogen atoms and one aromatic hydrogen, but not
between the thiomethyl and pentamethylcyclopentadie-
nyl hydrogen atoms, suggesting that the thiomethyl
group is trans to the cyclopentadienyl ring, as for the
rhodium analogue [11,12]. The cation of 8 contains three
stereogenic centres: the iridium, sulfur and phosphorus
atoms. In rhodium complexes of Cp–PL ligands the
configurations at the metal and phosphorus are fixed
relative to each other by the ligand’s geometry such that
the non-ligating substituent of the phosphine and the
halide are on the same side of the plane defined by the
metal and phosphorus atoms and the cyclopentadienyl
centroid [12]. Presumably the same argument is valid for
8. This, together with the exclusively trans disposition of
the thiomethyl and pentamethylcyclopentadienyl
groups, leads to the existence of only the RIrRSSP and
SIrSSRP pair of enantiomers.
NMR spectra of 10a are similar to those of the rhodium
analogue [12] and the 31P{1H} NMR spectrum exhibits
a singlet at d )9.1. The 19F and 31P{1H} NMR spectral
properties of 10b are similar to those of 10a. In situ
NMR studies indicate 10a and 10b undergo slow reac-
tions in the presence of proton sponge. The NMR data
are fully consistent with intramolecular dehydrofluor-
inative coupling to give 11a and 11b. In particular, the
19F NMR spectra show four resonances in addition to
those of tetrafluoroborate with values of d similar to
those of the rhodium analogue ()119.22, )136.07,
)145.54 and )152.01 [12]). Both 31P{1H} NMR spectra
exhibit a singlet resonance at ca. d 5. The shift of ca. 15
ppm to higher frequency on coupling is similar to that of
18.3 ppm observed in the rhodium analogue of 11a [12].
The 1H NMR spectrum of 11a exhibits the two expected
methylene resonances at d 3.85 (dd) and 3.64 (dd), and
four methyl resonances at d 2.30 (d), 1.90 (d), 1.73 (d)
and 1.51 (s), which are at similar chemical shifts to those
of the rhodium analogue (d 2.08, 1.82, 1.71 and 1.52).
BF4
RNC, NaBF4,
Ir
Cl
Ir
Cl
PPh2(C6F5)
CH2Cl2/MeOH
PPh2(C6F5)
Cl
RNC
10a R = Ph
10b R = CMe3
9
proton sponge,
CDCl3 or CH2Cl2
BF4
F
F
Ir
F
Ir
F
Cl
Cl
Cl
P
P
RNC
F
F
Ph
Ph
Ph
Ph
F
F
11a R = Ph
11b R = CMe3
Scheme 2.

2664
R.M. Bellabarba, G.C. Saunders / Polyhedron 23 (2004) 2659–2664
[5] Y. Kataoka, Y. Iwato, A. Shibahara, T. Yamagata, K. Tani,
Chem. Commun. (2000) 841.
Although methylene resonances at d 3.75 (m) and 3.46
(m), and two methyl resonances at d 2.18 (d) and 1.85
(d) are evident in the H NMR spectrum of 11b, the
[6] Y. Kataoka, A. Shibahara, T. Yamagata, K. Tani, Organomet-
allics 20 (2001) 2431.
1
other resonances are obscured by other products and the
proton sponge resonances. The reaction of 10a is rea-
sonably clean, but that of 10b is not and 11b is produced
in ca. 50% yield. The identities of 11a and 11b were
confirmed by mass spectrometry. The values of m(NBC)
for 11a and 11b were identical within experimental error
to those of 10a and 10b respectively. The coupling re-
action of 10a was also performed on a preparative scale
giving 11a as a yellow–brown solid in 81% yield.
[7] K. Onitsuka, N. Dodo, Y. Matsushima, S. Takahashi, Chem.
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€
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The intramolecular dehydrofluorinative coupling of
pentamethylcyclopentadienyl and pentafluorophenyl-
phosphine ligands can be accomplished in cationic
iridium complexes by treatment with less than one
equivalent of proton sponge. The fluoride generated as
the byproduct is sufficient to facilitate the reaction. The
reaction occurs slowly for complexes of monophos-
phines to give bifunctional g5,jP-Cp–P ligands, but is
more successful for complexes of chelating phosphine
ligands, which give trifunctional g5,jP,jL-Cp–PL li-
gands rapidly. The reported reactions are identical to
those of the rhodium analogues.
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We thank the E.P.S.R.C. for support (to R.M.B.), the
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