A high-yield synthetic approach to trans-[Ir(ER3)2(CO)X] (ER3=PMe3, PEt3, PPhMe2, PPh2Me, P(OMe)3, AsMe3, AsEt3, AsPh3, SbPh3; X=Cl, Br)

Article abstract of DOI:10.1016/S0277-5387(99)00225-9

The complex [Ir(CO)₂X₂][NBu₄] (X=Cl, Br) forms Vaska-type complexes, trans-[Ir(ER₃)₂(CO)X], when treated with two equivalents of aryl- or alkyl-phosphines, arsines, or stibines under a CO atmosphere. The synthesis is general for a wide range of phosphines, arsines, or stibines irrespective of the cone angle. For small cone-angle ligands, the initial addition of ligand to [Ir(CO)₂X₂][NBu₄] is performed at low temperature. The synthesis and characterisation of three new Vaska-type complexes trans-[Ir(P(OMe)₃)₂(CO)Cl], trans-[Ir(AsMe₃)₂(CO)Cl], and trans-[Ir(AsEt₃)₂(CO)Cl] is also reported. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00225-9

Polyhedron 18 (1999) 3031–3034
www.elsevier.nl/locate/poly
A high-yield synthetic approach to trans-[Ir(ER3)2(CO)X] (ER35PMe3,
PEt3, PPhMe2, PPh2Me, P(OMe)3, AsMe3, AsEt3, AsPh3, SbPh3;
X5Cl, Br)
*
Leslie D. Field , Eric T. Lawrenz, Antony J. Ward
School of Chemistry, University of Sydney, Sydney, N.S.W. 2006, Australia
Received 17 June 1999; accepted 29 July 1999
Abstract
The complex [Ir(CO)2X2][NBu4] (X5Cl, Br) forms Vaska-type complexes, trans-[Ir(ER3)2(CO)X], when treated with two equivalents
of aryl- or alkyl-phosphines, arsines, or stibines under a CO atmosphere. The synthesis is general for a wide range of phosphines, arsines,
or stibines irrespective of the cone angle. For small cone-angle ligands, the initial addition of ligand to [Ir(CO)2X2][NBu4] is performed
at low temperature. The synthesis and characterisation of three new Vaska-type complexes trans-[Ir(P(OMe)3)2(CO)Cl], trans-
[Ir(AsMe3)2(CO)Cl], and trans-[Ir(AsEt3)2(CO)Cl] is also reported.
1999 Elsevier Science Ltd. All rights reserved.
Keywords: Vaska-type complexes; Iridium(I); Synthesis
1. Introduction
phosphine complexes [Ir(dppe)(CO)X] (dppe51,2-bis-
(diphenylphosphino)ethane; X5Cl, Br).
One of the most widely studied classes of iridium(I)
complexes is that represented by Vaska’s complex trans-
[Ir(PPh3)2(CO)C1] [1–10] and its analogues. The interest
in these complexes results from the importance of the
oxidative-addition reactions that were originally discovered
in this series [1–10].
A convenient synthesis of Vaska-type complexes from
[Ir(cod)Cl]2 and a wide range of phosphines was reported
by Crabtree et al. [11,12]. However, this approach has two
significant drawbacks: (i) the synthesis of the precursor
complex [Ir(cod)Cl]2 is achieved in highly variable yield;
and (ii) the method requires modification for small cone
angle phosphines, such as PMe3 [11,12].
Here we report a synthesis of iridium(I) complexes of
the general formula trans-[Ir(ER3)2(CO)X] (ER35PMe3,
PEt3, PPhMe2, PPh2Me, P(OMe)3, AsMe3, AsEt3, AsPh3,
SbPh3; X5Cl, Br), from [Ir(CO)2X2][NBu4], which is
general for all phosphines, arsines, and stibines. The route
is based upon the procedure employed by Fisher and
Eisenberg [13] for the synthesis of the cis-coordinated
2. Experimental section
The manipulation and synthesis of air-sensitive phos-
phines, arsines, stibines, and metal complexes was per-
formed under an atmosphere of nitrogen or carbon monox-
ide using standard Schlenk or vacuum line techniques.
Tetrahydrofuran (THF) and diethyl ether were obtained
from BDH and were dried over sodium wire before
distillation from sodium/benzophenone. Ethanol was dis-
tilled from diethoxymagnesium. Trimethylphosphine, di-
methylphenylphosphine, diphenylmethylphosphine, tri-
ethylphosphine, and trimethylphosphite were obtained
from Aldrich Co. and used without further purification.
Triphenylarsine, triethylarsine, trimethylarsine, and tri-
phenylstibine were obtained from Strem Chemicals Inc.
and were used without further purification. Iridium tri-
chloride trihydrate was obtained from Johnson Matthey
Co. All compressed gases were obtained from B.O.C.
Gases. Nitrogen (.99.5%) and carbon monoxide
(.99.0%) were used as received without further purifica-
tion.
*Corresponding author. Tel.: 161-29-351-2060; fax: 161-29-351-
6650.
E-mail address: l.field@chem.usyd.edu.au (L.D. Field)
Air-sensitive NMR samples were prepared in a nitrogen
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00225-9
1999 Elsevier Science Ltd. All rights reserved.

3032
L.D. Field et al. / Polyhedron 18 (1999) 3031–3034
filled dry-box, with the solvent vacuum transferred into an
NMR tube fitted with a concentric teflon valve. 1H, 31P, and
13C NMR spectra were recorded on a Bruker DRX400
spectrometer at 400.13, 161.98, and 100.62 MHz, respec-
tively.
Mass spectra were recorded using chemical ionisation
(CI) on a Finnigan MAT TSQ-46 equipped with a
desorption probe with a source temperature of 1408C and
an electron energy of 100 eV. The ionisation gas was
methane. In all cases, M represents the molecular ion and
L represents the ligand ER3.
2.3. Trans-
carbonylchlorobis(trimethylphosphine)iridium(I)
The metal complex was purified by sublimation at 608C
(0.06 Torr). The title complex was obtained as a bright
yellow microcrystalline solid (81 mg, 75%). IR (Nujol),
n(CO): 1943 (vs) cm21. 1H NMR (benzene-d6): d 1.26 (m,
splitting53.6 Hz, CH3) ppm. 31Ph1Hj NMR (benzene-d6):
d 219.2 (s) ppm. Infrared, 31Ph1Hj and H NMR were in
1
good agreement with the literature [14,15].
Melting points of air-sensitive samples were determined
in a sealed capillary using a Gallenkamp melting point
apparatus and are uncorrected. Infrared spectra were
recorded using a Perkin-Elmer 1600 Series FTIR spec-
trometer, the samples being run as Nujol mulls with NaCl
plates.
2.4. Trans-bromocarbonylbis(triethylphosphine)iridium(I)
The metal complex was purified by sublimation at 608C
(0.06 Torr). The title complex was obtained as a bright
yellow microcrystalline solid (85 mg, 60%). IR (Nujol),
n(CO): 1941 (vs) cm21. 1H NMR (benzene-d6): 61.88 (m,
12H, CH2), 0.98 (m, splitting58.0 Hz, 18H, CH3) ppm.
31Ph1Hj NMR (benzene-d6): d 17.3 (s) ppm. Infrared data
was in good agreement with that reported in the literature
[15].
The
syntheses
of
[Ir(CO)2Cl2][NBu4]
and
[Ir(CO)2Br2][NBu4] were based upon the method de-
scribed by Fisher and Eisenberg [13].
2.1. General preparation of trans-[Ir(ER3 )2(CO)X]
(ER35PPh2Me, PPhMe2 , PMe3 , PEt3 , P(OMe)3 , AsPh3 ,
AsEt3 , AsMe3 , SbPh3 ; X5Cl, Br)
2.5. Trans-carbonylchlorobis(triethylphosphine)iridium(I)
The metal complex was purified by sublimation at 608C
(0.06 Torr). The title complex was obtained as a bright
yellow microcrystalline solid (102 mg, 78%). IR (Nujol),
A solution of the appropriate ligand ER3(0.530 mmol)
in THF (5 ml) was added to
a
solution of
[Ir(CO)2X2][NBu4] (0.265 mmol) in THF (20 ml) under a
CO atmosphere with vigorous stirring. In the case of the
small cone angle ligands, the [Ir(CO)2X2][NBu4] solution
was cooled to 2788C, a chilled solution of the ligand was
added dropwise and the reaction mixture was stirred for 1
h at this temperature. After addition was complete the
reaction mixture was stirred at room temperature for 1 h.
In the case of the large cone angle ligands (PPhMe2,
PPh2Me, AsPh3, SbPh3) the solvent was removed under
vacuum, and ethanol (15 ml) was added. The solvent was
reduced under vacuum until precipitation of the metal
complex was complete.
In the case of the small cone angle ligands (PMe3, PEt3,
P(OMe)3, AsMe3, AsEt3) the solvent was reduced under
vacuum and the residue was extracted with ether. The
solvent was removed under vacuum, and the metal com-
plex was purified by sublimation.
1
n(CO): 1944 (vs) cm21. H NMR (benzene-d6): d 1.81
(multiplet, 12H, CH2), 1.00 (m, splitting58.0 Hz, 18H,
CH3) ppm. 31Ph1Hj NMR (benzene-d6): d 19.7 (s) ppm.
Infrared data was in good agreement with that reported in
the literature [15].
2.6. Trans-
bromocarbonylbis(dimethylphenylphosphine)iridium(I)
The title complex was obtained as a bright yellow
microcrystalline solid (99 mg, 65%) by precipitation from
1
ethanol. IR (Nujol), n(CO): 1950 (vs) cm21. H NMR
(benzene-d6): d 7.48 (m, 4H, o-H), 7.36 (m, 6H, m-, p-H),
1.64 (m, 12H, splitting53.9 Hz, CH3) ppm. 31Ph1Hj NMR
(benzene-d6): d 28.4 (s) ppm. Infrared data was in good
agreement with that reported in the literature [15].
2.2. Trans-
2.7. Trans-
bromocarbonylbis(trimethylphosphine)iridium(I)
carbonylchlorobis(dimethylphenylphosphine)iridium(I)
The metal complex was purified by sublimation at 608C
(0.06 Torr). The title complex was obtained as a bright
yellow microcrystalline solid (86 mg, 72%). IR (Nujol),
The title complex was obtained as a bright yellow
microcrystalline solid (104 mg, 74%) by precipitation from
1
ethanol. IR (Nujol), n(CO): 1954 (vs) cm21. H NMR
1
n(CO): 1951 (vs) cm21. H NMR (benzene-d6): d 1.31
(benzene-d6): d 7.67 (m, 4H, o-H), 7.03 (m, 6H, m-, p-H),
1.65 (m, 12H, splitting53.4 Hz, CH3) ppm. 31Ph1Hj NMR
(benzene-d6): d 25.6 (s) ppm. Infrared data was in good
agreement with that reported in the literature [15].
(multiplet, splitting54.0 Hz, CH3). 31Ph1Hj NMR
(benzene-d6): d 218.6 (s) ppm. Infrared and the 31Ph1Hj
NMR were in good agreement with the literature [8].

L.D. Field et al. / Polyhedron 18 (1999) 3031–3034
3033
2.8. Trans-
p-H) ppm. Infrared data was in good agreement with that
carbonylchlorobis(diphenylmethylphosphine)iridium(I)
reported in the literature [15].
The title complex was obtained as a bright yellow
microcrystalline solid (122 mg, 70%) by precipitation from
2.13. Trans-carbonylchlorobis(triphenylstibine)iridium(I)
1
ethanol. IR (Nujol), n(CO): 1950 (vs) cm21. H NMR
The title complex was obtained as a yellow mi-
crocrystalline solid (168 mg, 66%) by precipitation from
(benzene-d6): d 7.97 (m, 8H, o-H), 7.28 (m, 12H, m-,
p-H), 2.36 (s, 6H, CH3) ppm. 31Ph1Hj NMR (benzene-d6):
d 5.20 (s) ppm. Infrared data was in good agreement with
that reported in the literature [16].
1
ethanol. IR (Nujol), n(CO): 1953 (vs) cm21. H NMR
(benzene-d6): d 7.77 (m, 12H, o-H), 7.01 (m, 18H, m-,
p-H) ppm. Infrared data was in good agreement with that
reported in the literature [15].
2.9. Trans-
carbonylchlorobis(trimethylphosphite)iridium(I)
3. Results and discussion
The metal complex was purified by sublimation at 608C
(0.06 Torr). The title complex was obtained as a bright
yellow microcrystalline solid (101 mg, 65%), m.p. 186–
1878C (dec). IR (Nujol), n(CO): 1988 (vs) cm21. 1H NMR
(benzene-d6): d 3.55 (m, splitting55.9 Hz) ppm. 31Ph1Hj
The method for the synthesis for complexes of the
formula trans-[Ir(ER3)2(CO)X] is shown in Eq. (1). This
method is general for a large range of Group 15 ligands.
The ligands examined here were PPh2Me, PPhMe2, PMe3,
PEt3, P(OMe)3, AsPh3, AsEt3, AsMe3, and SbPh3.
1
NMR (benzene-d6): d 124.4 (s) ppm. 13Ch31P, Hj NMR
(benzene-d6): d 169.8, 52.5 ppm. m/z (CI, CH4): 505
(MH1, 57%), 477 ([IrL2(CO)]H1, 100), 125 (LH1, 82).
Anal. Calcd. C7H18ClIrO7P2: C, 16.69; H, 3.61. Found: C,
16.9; H, 3.7.
[Ir(CO)2X2][NBu4] 1 2ER3 → [Ir(ER3)2(CO)X]
1 [NBu4]X 1 CO (1)
The precursor complexes, [Ir(CO)2X2][NBu4], were syn-
thesised in high yield by refluxing IrCl3?3H2O in formic
acid and hydrochloric acid (for X5Cl) or refluxing in a
mixture of formic acid, hydrobromic acid, and potassium
bromide (for X5Br). [Ir(CO)2X2][NBu4] was precipitated
by the addition of tetrabutylammonium chloride and
recrystallisation from isopropanol afforded the complexes
as moderately air-stable, yellow crystalline solids.
The reaction to produce Vaska-type complexes involves
the slow addition of the alkyl- or aryl-phosphine, arsine, or
stibine to a THF solution of [Ir(CO)2X2][NBu4] under a
CO atmosphere. In the case of the small cone angle ligands
(i.e. PMe3, PEt3, P(OMe)3, AsMe3 and AsEt3), the
reaction mixture was cooled to 2788C then slowly
warmed to room temperature upon addition of the ligands.
The reaction mixture was stirred for 1 h at room tempera-
ture, before the solvent was reduced in vacuo. During the
removal of the solvent the original pale yellow solutions
darkened in colour to bright yellow, which is the result of
2.10. Trans-carbonylchlorobis(trimethylarsine)iridium(I)
The metal complex was purified by sublimation at 608C
(0.06 Torr). The title complex was obtained as a bright
yellow microcrystalline solid (89 mg, 68%), m.p. 186–
1878C (dec). IR (Nujol), n(CO): 1928 (vs) cm21. 1H NMR
(benzene-d6): d 1.18 (s) ppm. 13Ch1Hj NMR (benzene-d6):
d 171.5, 10.5 ppm. m/z (CI, CH4): 497 (MH1, 44%), 461
([IrL2(CO)]H1, 8), 121 (LH1, 100). Anal. Calcd.
C7H,8As2ClIrO: C, 16.96; H, 3.66. Found: C, 17.2; H, 3.8.
2.11. Trans-carbonylchlorobis(triethylarsine)iridium(I)
The metal complex was purified by sublimation at 608C
(0.06 Torr). The title complex was obtained as a bright
yellow microcrystalline solid (128 mg, 83%), m.p. 74–
758C. IR (Nujol), n(CO): 1939 (vs) cm21 1H NMR
.
(benzene-d6): d 1.78 (q, 3J57.8 Hz, 12H, CH2), 1.08 (t,
3J57.8 Hz, 18H, CH3) ppm. 13Ch1Hj NMR (benzene-d6):
d 170.9, 15.4, 9.6 ppm. m/z (CI, CH4): 581 (MH1, 11%),
545 ([IrL2(CO)]H1, 1), 163 (LH1, 100). Anal. Calcd.
C13H30As2ClIrO: C, 26.93; H, 5.21. Found: C, 27.2; H,
5.1.
the loss of
a
carbonyl group from the species
[Ir(ER3)2(CO)2X] [2].
The isolation of the products was achieved by the
addition of dry ethanol followed by reduction of the
solvent in vacuo until precipitation of the complexes was
complete.
In
the
case
of
the
complexes
2.12. Trans-carbonylchlorobis(triphenylarsine)iridium(I)
[Ir(PMe3)2(CO)Cl], [Ir(PEt3)2(CO)Cl], [Ir(PEt3)2(CO)-
Br], [Ir(P(OMe)3)2(CO)Cl], [Ir(AsMe3)2(CO)Cl] and
[Ir(AsEt3)2(CO)Cl], the solvent was removed under vac-
uum, the residue was extracted with ether, the ether was
removed under vacuum, and the complex purified by
sublimation at 608C (0.06 Torr). Physical and spectro-
The title complex was obtained as a yellow mi-
crocrystalline solid (159 mg, 69%) by precipitation from
1
ethanol. IR (Nujol), n(CO): 1940 (vs) cm21. H NMR
(benzene-d6): d 7.87 (s, 12H, o-H), 7.01 (bs, 18H, m-,

3034
L.D. Field et al. / Polyhedron 18 (1999) 3031–3034
[4] L. Vaska, Acc. Chem. Res. 1 (1968) 335, and references therein.
[5] J. Halpern, Acc. Chem. Res. 3 (1970) 386, and references therein.
[6] F. Glocking, J.G. Irwin, Inorg. Chim. Acta 6 (1972) 355, and
references therein.
scopic data for known complexes were in good agreement
with literature data.
[7] E.A.V. Ebsworth, D.M. Leitch, J. Chem. Soc., Dalton Trans. 1973,
1287.
[8] R.W. Marks, S.S. Wreford, D.D. Traficante, Inorg. Chem. 17 (1978)
756.
[9] E.A.V. Ebsworth, T.E. Fraser, J. Chem. Soc., Dalton Trans. 1979,
1960.
[10] M.A. Bennett, G.T. Crisp, Organometallics 5 (1986) 1800.
[11] M.J. Burk, R.H. Crabtree, Inorg. Chem. 25 (1986) 931.
[12] X.-L. Luo, D. Michos, R.H. Crabtree, M.B. Hall, Inorg. Chim. Acta
198–200 (1992) 429.
Acknowledgements
We gratefully acknowledge financial support from the
Australian Research Council and the Australian Govern-
ment for an Australian Postgraduate Award (AJW). We
also thank Johnson Matthey Pty. Ltd. for the generous loan
of iridium salts.
[13] B.J. Fisher, R. Eisenberg, Inorg. Chem. 23 (1984) 3216.
[14] J.A. Labinger, J.A. Osborn, Inorg. Synth. 18 (1978) 62.
[15] G.J. Leigh, R.L. Richards, in: G. Wilkinson, F.G.A. Stone, E.W.
Abel (Eds.), Comprehensive Organometallic Chemistry, Vol. 5,
Pergamon, Oxford, 1982, p. 549, Chap. 36, and references therein.
[16] J.P. Collman, J.W. Kang, J. Am. Chem. Soc. 89 (1967) 844.
References
[1] L. Vaska, J.W. DiLuzio, J. Am. Chem. Soc. 84 (1962) 1074.
[2] P.B. Chock, J. Halpern, J. Am. Chem. Soc. 88 (1966) 3511.
[3] J.P. Collman, Acc. Chem. Res. 1 (1968) 136, and references therein.