Reversible CO2 fixation by iridium(I) complexes containing Me2PhP as ligand

Article abstract of DOI:10.1021/om900918t

The iridium(I) complexes [IrCl(Me₂PhP)₃] (1), [Ir(Me₂PhP)₄]Cl (2), [Ir(Me₂PhP)₄]I (3), and [Ir(Me₂PhP)₄]PF₆ (4) are prepared from the iridium(I) precursors

Full text of DOI:10.1021/om900918t

1642 Organometallics 2010, 29, 1642–1651
DOI: 10.1021/om900918t
Reversible CO2 Fixation by Iridium(I) Complexes Containing
Me2PhP as Ligand
,†
Jens Langer,* Wolfgang Imhof, Maria Jose Fabra, Pilar Garcı
†
‡
‡
ꢀ
Helmar Gorls, Fernando J. Lahoz, Luis A. Oro,* and Matthias Westerhausen
~
´
a-Orduna,
†
‡
,‡
†
€
†Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-University Jena,
‡
August-Bebel-Strasse 2, 07747 Jena, Germany, and Departamento de Quımica Inorganica,
´
Instituto Universitario de Cataꢀlisis Homogeꢀnea, Instituto de Ciencia de Materiales de Aragoꢀn,
ꢀ
´
Universidad de Zaragoza-Consejo Superior de Investigaciones Cientıficas, 50009-Zaragoza, Spain
Received October 20, 2009
The iridium(I) complexes [IrCl(Me2PhP)3] (1), [Ir(Me2PhP)4]Cl (2), [Ir(Me2PhP)4]I (3), and [Ir(Me2-
PhP)4]PF6 (4) are prepared from the iridium(I) precursors [IrX(coe)2]2 (X = Cl, I). Complex 1 reacts
reversibly with CO2 to form the metallacyclic compound [IrCl(C2O4-κ2C,O)(Me2PhP)3] (5), which was
characterized by NMR and IR measurements as well as elemental analysis. Additionally, [mer-Ir(Cl)2-
(H)(Me2PhP)3] (6) and[mer-Ir(CO3)(H)(Me2PhP)3] (7) are formed as side products from water present in
the used CO2 and the solvents. Compound 2 yields similar results. When the iodo compound 3 is used, the
cationic compound [Ir(I)(H)(Me2PhP)4]þI- (9) is formed as one of the products. Molecular structures of
1, 2, 5, and 9 are presented.
Introduction
with CO2 involving C-H activation,8-11 and in the oxidative
coupling with an additional CO22 or O2.12,13
During the last decades, there has been a growing interest
in the application of CO2 as a C1 building block in the syn-
thesis of organic compounds. Although the possible positive
influence of such reactions in context of the greenhouse effect
is questionable, the use of cheap, nontoxic, and abundant
CO2 may offer new and efficient routes to fine chemicals, if
its relative inertness can be overcome. One of the possible
ways to realize this is the use of transition metal complexes
for CO2 activation and transformation.1
Initial investigations by Herskovitz and others have shown
that iridium is a very promising candidate in reactions
involving CO2.2,3
CO2 was successfully used as a ligand in iridium comp-
ounds showing different coordination modes3-6 (see Scheme 1),
and iridium compounds have been found to be active in the
catalytic hydrogenation of CO2,7 in carboxylation reactions
This metal-mediated coupling of two molecules of CO2,
leading to a stable metallacycle that shows no tendency of
reductive disproportionation to CO32- and CO, is unique to
iridium and to some extent to rhodium. The reaction was so
far limited to iridium complexes with Me3P as supporting
ligand. Unfortunately, the formed product was insoluble in
nonpolar organic solvents and decomposes in more polar
ones. This behavior prevents the investigation of this com-
pound in solution and the exploration of possible applica-
tions. Besides the Me3P-substituted iridium system, a similar
iridium compound with Me3As2 and two related rhodium
systems were mentioned,14,15 but no reliable data, except of
an elemental analysis in the case of one rhodium compound,
are available for those compounds. Herein we report on the
investigation of related Me2PhP-ligated iridium complexes.
Results and Discussion
Preparation and Characterization of the Iridium(I) Com-
pounds. [IrCl(Me2PhP)3] (1), [Ir(Me2PhP)4]Cl (2), [Ir(Me2-
PhP)4]I (3), and [Ir(Me2PhP)4]PF6 (4) were prepared from
*To whom correspondence should be addressed. E-mail: j.langer@
uni-jena.de (J.L.); oro@unizar.es (L.A.O.).
(1) For reviews see: (a) Walter, D. Coord. Chem. Rev. 1987, 79, 135–
174. (b) Behr, A. Angew. Chem. 1988, 100, 681–698. (c) Gibson, D. H.
Chem. Rev. 1996, 96, 2063–2095. (d) Braunstein, P.; Matt, D.; Nobel, D.
Chem. Rev. 1988, 88, 747–764. (e) Yin, X.; Moss, J. R. Coord. Chem. Rev.
1999, 181, 27–59. (f) Aresta, M.; Dibenedetto, A. Dalton Trans. 2007,
2975–2992.
(2) Herskovitz, T.; Guggenberger, L. J. J. Am. Chem. Soc. 1976, 98,
1615–1616.
(3) Herskovitz, T. J. Am. Chem. Soc. 1977, 99, 2391–2392.
(4) Lee, D. W.; Jensen, C. M.; Morales-Morales, D. Organometallics
2003, 22, 4744–4749.
(8) English, A. D.; Herskovitz, T. J. Am. Chem. Soc. 1977, 99, 1648–
1649.
(9) Behr, A.; Herdtweck, E.; Herrmann, W. A.; Keim, W.; Kipshagen,
W. J. Chem. Soc., Chem. Commun. 1986, 1262–1263.
(10) Behr, A.; Herdtweck, E.; Herrmann, W. A.; Keim, W.; Kipshagen,
W. Organometallics 1987, 6, 2307–2313.
~
(11) Langer, J.; Fabra, M. J.; Garcıa-Orduna, P.; Lahoz, F. J.; Oro,
´
L. A. Chem. Commun. 2008, 4822–4824.
(12) Lawson, H. J.; Atwood, J. D. J. Am. Chem. Soc. 1989, 111, 6223–
6227.
(5) Audett, J. D.; Collins, T. J.; Santarsiero, B. D.; Spies, G. H. J. Am.
Chem. Soc. 1982, 104, 7352–7353.
(6) Hanna, T. A.; Baranger, A. M.; Bergman, R. G. J. Am. Chem.
Soc. 1995, 117, 11363–11364.
(7) For a review see: The Handbook of Homogeneous Hydrogenation;
Wiley-VCH Verlag GmbH&Co. KGaA: Weinheim, 2007; pp 489-511.
(13) Mason, M. G.; Ibers, J. A. J. Am. Chem. Soc. 1982, 104, 5153–
5157.
(14) Herskovitz, T. Inorg. Synth. 1982, 21, 99–103.
(15) Dahlenburg, L.; Prengel, C. J. Organomet. Chem. 1986, 308, 63–71.
r
pubs.acs.org/Organometallics
Published on Web 03/18/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 7, 2010 1643
Figure 2. Molecular structure of [Ir(Me2PhP)4]Cl (50% proba-
bility level; H atoms are omitted for clarity). Selected bond dis-
tances (A) and bond angles (deg): Ir(1)-P(1) 2.2979(15), Ir(1)-
P(2) 2.3109(15), Ir(1)-P(3) 2.3047(14), Ir(1)-P(4) 2.2822(15),
P(1)-Ir(1)-P(2) 92.58(5), P(1)-Ir(1)-P(3) 152.78(5), P(1)-
Ir(1)-P(4) 92.66(5), P(2)-Ir(1)-P(3) 93.35(5), P(2)-Ir(1)-P(4)
155.84(5), P(3)-Ir(1)-P(4) 92.70(5).
Figure 1. Molecular structure of [IrCl(Me2PhP)3] (50% proba-
bility level; H atoms are omitted for clarity). Selected bond
distances (A) and bond angles (deg): Ir(1)-P(1) 2.2909(8), Ir(1)-
P(2) 2.2044(8), Ir(1)-P(3) 2.3112(8), Ir(1)-Cl(1) 2.4027(8), P(1)-
Ir(1)-P(2) 94.26(3), P(2)-Ir(1)-P(3) 94.38(3), P(1)-Ir(1)-P(3)
169.90(3), P(1)-Ir(1)-Cl(1) 88.14(3), P(2)-Ir(1)-Cl(1) 175.32(3),
P(3)-Ir(1)-Cl(1) 83.62(3).
Interestingly, the ionic compound 2 (see Figure 2) is also
slightly soluble in aromatic solvents such as benzene and
toluene. The 31P NMR spectrum in C6D6 reveals that this
solubility is due to the fluxional behavior of this compound
in solution, and only an extremely broad signal (more then
20 ppm) was observed. An equilibrium is active in benzene
solution, most likely involving the exchange of one phos-
phane ligand by the chloride anion (Scheme 3).
Scheme 1. CO2 Complexes of Iridium
The mainspring of this ligand exchange probably is the
reduction of steric pressure and the decrease of distortion of
the square-planar geometry around the iridium center. As
can be seen in Figure 2, compound 2 shows tetrahedral
distortion (by about 36°) from the expected square-planar
geometry and a distance of 0.5 A between the phosphorus
atoms and the mean plane (P1,P2,P3,P4). This distortion is
slightly smaller than found for [Ir(MePh2P)4]BF4 (40°)18,19
and [Ir(Me3P)4]PF6.20
In contrast to 2, compound 4, containing a weakly co-
ordinating anion, is insoluble in aromatic solvents and shows
a sharp 31P NMR signal at δ=-15.5 in deuterated acetone.
Reactivity of 1-4 toward CO2. When a solution of 1 in ben-
zene or toluene was exposed to a CO2 atmosphere, a signi-
ficant change of color from orange to yellow was observed.
Cooling to -40 °C (in toluene) results in a nearly colorless
solution, which turned back to yellow when warmed to room
temperature. This alteration of color suggests a reversible
CO2 uptake, depending on the CO2 concentration in solu-
tion. When the 31P NMR spectrum was measured after
several hours under CO2 atmosphere, a complex product
mixture was observed. Besides the starting material 1, one
main product (5) and three minor products (6-8) have been
Scheme 2
[IrX(coe)2] (X = Cl, I; coe = cyclooctene) and the adequate
amount of Me2PhP (for details see Experimental Section),
and crystalline solids were obtained in all cases. The crystal
and molecular structures of 1 and 2 were determined by
X-ray diffraction to doubtlessly ensure their composition.
The molecular structure of 1 is displayed in Figure 1 and
shows the iridium atom in a slightly distorted square-planar
environment in agreement with similar compounds.16,17 The
angles P1-Ir-P2 and P3-Ir-P2 are slightly enlarged to
94.36° and 94.26° due to the steric requirements of the phos-
phane ligands, while the angles P1-Ir-Cl and P3-Ir-Cl are
smaller than 90° (88.15° and 83.63°).
The solid-state structure is maintained in solution as jud-
ged by the 31P NMR spectrum of the compound in C6D6.
A sharp doublet at -7.1 ppm and a triplet at -23.2 ppm with
relative intensities of two to one and a coupling constant of
25.3 Hz were observed as expected for a square-planar
iridium(I) compound.
(18) Clark, G. R.; Skelton, B. W.; Waters, T. N.; Davies, J. E. Acta
Crystallogr. 1987, C43, 1708–1709.
(19) Clark, G. R.; Skelton, B. W.; Waters, T. N. J. Organomet. Chem.
1975, 85, 375–394.
(20) Blum, O.; Calabrese, J. C.; Frolow, F.; Milstein, D. Inorg. Chim.
Acta 1990, 174, 149–151.
(16) Simons, R. S.; Panzner, M. J.; Tessier, C. A.; Youngs, W. J.
J. Organomet. Chem. 2003, 681, 1–4.
(17) Orpen, A. G.; Pringle, P. G.; Smith, M. B.; Worboys, K.
J. Organomet. Chem. 1998, 550, 255–266.

1644 Organometallics, Vol. 29, No. 7, 2010
Langer et al.
Figure 3. 31P NMR spectra of the starting material 1 (top) in C6D6, 1 under CO2 atmosphere for 5 h (middle), and 1 under CO2 atmos-
phere for 96 h (bottom) (*impurity).
Scheme 3. Equilibrium between 1 and 2
Scheme 4. Comparison of Selected 13C NMR Data (δ) of 5 and
formed, as judged by the observed NMR data (Figure 3). If
measured after a longer reaction time, the signals of the start-
Related Compounds21-23
ing material have decreased in intensity, as have the signals of
the former main product 5, which is in equilibrium with 1 and
CO2. The final product mixture contained two major pro-
ducts (6 and 7) and a minor product (8).
Besides toluene, benzene and thf are suitable solvents for
this reaction. The isolated final product mixtures contain
6-8 in slightly different ratios, depending on the solvent used
and CO2 pressures applied.
Compound 5 was identified as [mer-IrCl(C2O4-κ2C,O)-
(Me2PhP)3] (Scheme 4), containing a newly formed ligand
derived by reductive coupling of two CO2 molecules. The
assignment is based on the following observations. If the
reactants are suspended in ether, the originally yellow color
of the starting material slowly lightens and a white solid is
obtained. After repeated extractions with boiling ether, the
remaining solid shows vibrational bands of the formed unit
at 1727(s), 1686(vs), 1278(s), and 999(m) cm-1 in the infrared
spectrum, in good agreement with the bands reported for the
related [mer-IrCl(C2O4-κ2C,O)(Me3P)3] (1725(s), 1680(s),
1648(sh), 1605(m), 1290(s), 1005(m) cm-1).2 Additionally,
a peak with an iridium isotopic pattern at m/z = 695 in the
MALDI MS spectrum was observed, consistent with the
fragment “[Ir(C2O4)(Me2PhP)3]” [Mþ - Cl]. The molecular
peak was not observed. Finally, suitable crystals of 5 were
grown directly from the reaction mixture in dimethoxy-
ethane at room temperature (see Figure 4).
As shown in Figure 4, compound 5 has octahedral geo-
metry with the phosphane ligands in meridional arrange-
ment. Bond lengths and angles within the metallacyclic
moiety are in good agreement with the reported ones for
the Me3P derivative; only the bonds C(2)-O(3) (1.433(6) A)
(lit. 1.39(2) A) and C(1)-O(1) (1.288(6) A) (lit. 1.24(1) A) are
elongated.2
The compound is not stable in CD2Cl2 solution, but if a
pure sample is dissolved and rapidly measured, the 31P NMR
spectrum confirms that 5 is indeed the major species in
solution. The starting material 1 was detected among the
decomposition products.
NMR data of 5 were extracted from the measurement of
the reaction mixture of 1 and CO2. Two signals, a doublet at
δ=-31.3 and a triplet at δ=-41.0, with relative intensities
of two to one were observed for 5 in the 31P NMR spectra,
consistent with a meridional arrangement of the three phos-
phane ligands.
In addition, two signals for the metallacyclic moiety were
observed in the 13C NMR spectrum. A pseudoquartet at δ=
159.3 was assigned to the iridium-bound carbon atom.
A comparison with organic analogues of 5 revealed a high-
field shift of the signal of this carbon atom, as detected in
related iridium(III) complexes too (see Scheme 4). The obser-
2
ved cis-coupling constant JC,P of 6.4 Hz is in good agree-
ment with the one observed for [Ir{C(O)OMe}{C(CO2Me)d
CH[C(O)OMe]}(PPh3)(“PNH”)] (2JC,P = 7.6 Hz).21 The
13C resonance of the second carbon atom of the metallacycle,

Article
Organometallics, Vol. 29, No. 7, 2010 1645
Figure 5. Part of the 13C NMR spectrum of 5.
Scheme 5. Alternative Route to 6 and 7
Table 1. Comparison of IR Bands of the Product Mixture 6-8
with Selected Carbonate Compounds and CO2 Complexes
Figure 4. Molecular structure of complex 5 (30% probability
level; H atoms are omitted for clarity). Selected bond distances
(A) and bond angles (deg): Ir(1)-C(2) 1.974(5), Ir(1)-O(1)
2.117(3), Ir(1)-P(1) 2.3599(11), Ir(1)-P(2) 2.2738(11), Ir(1)-
P(3) 2.3700(12), Ir(1)-Cl(1) 2.4566(11), O(1)-C(1) 1.288(6),
O(2)-C(1) 1.228(6), O(3)-C(1) 1.369(6), O(3)-C(2) 1.433(6),
O(4)-C(2) 1.216(6), C(2)-Ir(1)-O(1) 79.89(16), C(2)-Ir(1)-
P(2) 93.86(14), C(2)-Ir(1)-P(1) 96.57(14), C(2)-Ir(1)-
P(3) 90.83(13), C(2)-Ir(1)-Cl(1) 169.49(14), O(1)-Ir(1)-P(1)
86.93(9), O(1)-Ir(1)-P(2) 173.69(9), O(1)-Ir(1)-P(3) 82.40(9),
O(1)-Ir(1)-Cl(1) 89.82(9).
entry
compound
vas(CdO) [cm-1
]
literature
1
2
3
4
5
6
compound 7
[(tdpme)IrCl(CO3)]
[(p-tolyl3P)2IrMe(CO)(CO3)]
[(Me2PhP)2RhCl(CO2)]
[(MePh2P)2Pd(CO2)]
[(Et3P)2Ni(CO2)]
1665, 1630
1665, 1620
1675, 1620
1657, 1627
1658, 1634
1660, 1635
36
12
37
38
39
tively assigned to this compound. This assignment is based
on the following observations. The product mixture contain-
ing 6-8 shows a signal at δ = 169.1 in the 13C NMR spec-
trum (C6D6), which is in good agreement with other iridium
carbonates such as [Ir(C7H4NS2)(CO3)(PPh3)2] (δ 167.1).29
The observed bands at 1665 and 1630 cm-1 in the IR spec-
trum also fit well to the ones reported for [IrCl(CO3)(tdpme)]
(1665 þ 1620 cm-1) (see Table 1). Finally, [mer-Ir(CO3)(H)-
(Me2PhP)3] was prepared by the reaction of 6 with Ag2CO3
in acetone to exclude doubts (see Scheme 5). The isolated
a doublet at δ = 158.8, concurs with the observed struc-
ture.
In contrast to the Me3P system, where no reversibility was
reported, the formation of 5 from 1 is reversible and depends
on the CO2 concentration in solution. This different beha-
vior may be due to the lower basicity of Me2PhP compared to
Me3P, therefore facilitating the decoupling of 5 to restore 1.
A reductive disproportionation of the formed metallacycle
into CO and CO32- was not observed, although such metal-
lacycles are among the proposed intermediates for this reac-
tion of transition metal/CO2 systems.24-26 Neither the reac-
tion solution nor the other products 6-8 contain CO, as
judged by IR and NMR measurements.
Besides 5, complex 6 was isolated from the final reaction
mixture by extraction with diethyl ether, in which it is slightly
soluble. 6 was identified as [mer-cis-IrCl2(H)(Me2PhP)3] by
comparison of its NMR signals with an authentic sample,
independently prepared by reaction of 1 with HCl in toluene
(Scheme 5). This compound was first reported by Jenkins
and Shaw,27 and the crystal structure was published by Robert-
son and Tucker.28
product shows the same 31P NMR signals as 7 in C6D6. A 13
C
NMR spectrum measured in d8-thf shows a doublet (J =
3.2 Hz) at δ=169.2 for the carbonate moiety. The chemical
shift and the observed coupling constants of the hydride
2
2
1
signal (δ = -21.89, J = 21.6 Hz, J = 15.6 Hz) in the H
NMR spectrum are also in agreement with the postulated
structure of 7.
If the preparation of [mer-Ir(CO3)(H)(Me2PhP)3] is car-
ried out in CH2Cl2 instead of acetone, a mixture of 7 and 8 is
obtained. In addition, 7 slowly transforms to 8 in CH2Cl2.
Therefore, the composition [mer-Ir(Cl)(CO3)(Me2PhP)3]
was preliminary assigned to 8, but this assignment remains
uncertain. Scheme 6 summarizes the observed products in
the reaction of 1 and CO2.
Probably, the observed products 6 and 7 arise from trace
amounts of water. Similarly, a iridium bicarbonate was
formed in the reaction of [IrH2{C6H3-2,6-(CH2PBut2)2}]
and CO2 from the water vapor, present in the used CO2
gas.4 The initial step of the reaction might be the well-known
oxidative addition of water to such electron-rich iridium(I)
complexes,30 followed by insertion of CO2 into the Ir-O
bond. However, an oxidative addition of preformed H2CO3
The remaining product mixture consists mainly of 7, and
the composition [mer-Ir(CO3)(H)(Me2PhP)3] can be tenta-
(21) Dahlenburg, L.; Herbst, K. J. Chem. Soc., Dalton Trans. 1999,
3935–3939.
(22) Tang, L.; Deng, L. J. Am. Chem. Soc. 2002, 124, 2870–2871.
(23) Kalinowski, H.-O.; Berger, S.; Braun, S. 13C-NMR-Spektrosko-
pie; Georg Thieme Verlag: Stuttgart, 1984.
ꢀ
(24) Carmona, E.; Gonzalez, F.; Poveda, M. L.; Marin, J. M.;
Atwood, J. L.; Rogers, R. D. J. Am. Chem. Soc. 1983, 105, 3365–3366.
(25) Karsch, H. H. Chem. Ber. 1977, 110, 2213–2221.
(26) Kempe, R.; Sieler, J.; Walther, D.; Reinhold, J.; Rommel, K.
Z. Anorg. Allg. Chem. 1993, 619, 1105–1110.
ꢀ
ꢀ
(29) Ciriano, M. A.; Lopez, J. A.; Oro, L. A.; Perez-Torrente, J. J.
(27) Jenkins, J. M.; Shaw, B. L. J. Chem. Soc. 1965, 6789–6796.
(28) Robertson, G. B.; Tucker, P. A. Aust. J. Chem. 1988, 41 (3), 283–
291.
Organometallics 1995, 14, 4764–4775.
(30) Blum, O.; Milstein, D. J. Am. Chem. Soc. 2002, 124, 11456–
11467.

1646 Organometallics, Vol. 29, No. 7, 2010
Langer et al.
Scheme 6
to the iridium(I) species also has to be considered. The
resulting iridium bicarbonate compound should be able to
react with another equivalent of 1 to form a binuclear
carbonate-bridged species. Finally, ligand redistribution
leads to formation of 6 and 7. Evidence for such a redis-
tribution reaction was obtained by NMR measurement of
the reaction mixture. At lower temperatures (223 K) an
additional product was observed that seems to reversibly
form at the expense of 6 and 7. This compound shows a
hydride signal in the 1H NMR spectra at δ=-19.5 (dt) with
coupling constants of 11.8 and 19.6 Hz. In the 31P NMR
spectra two signals at δ = -21.3 (d) and -35.2 (t) with a
coupling constant of 19.9 Hz and relative intensities of two to
one were found pointing toward a meridional arrangement
of three phosphane ligands. On basis of the observed data a
binuclear complex of the composition [{IrH(Cl)(Me2PhP)3}2-
( μ-CO3)] is postulated for this species. When the sample is
warmed to room temperature, the signals of this species
disappear and the relative amounts of 6 and 7 increase.
During this process not only the signals of 6 and 7 but also
the signals of 1 are broadened, indicating its participation in
this ligand exchange.
An alternative pathway to iridium carbonates via transi-
ent formiates, which are able to eliminate CO and subse-
quently form reactive hydroxo species, as observed in the
case of a similar iridium complex, can be excluded.31 For-
mation of CO or of CO complexes such as [IrCl2(CO)(H)-
(PMe2Ph)2] or [IrCl(CO)(PMe2Ph)2]32-34 was not detected
by infrared measurement or by prolonged 13C NMR mea-
surement (100 000 scans).
Attempts to completely exclude water from the reaction
mixture failed so far. Additional drying of the solvents and
working in more concentrated solutions result in lower
relative amounts of the byproducts 6-8, but their formation
could not be suppressed completely. However, these adjust-
ments made possible the isolation of 5 as a pure and crystal-
line solid in good yields (see Experimental Section).
If [Ir(Me2PhP)4]Cl (2) is used as starting material, a similar
product mixture (6-8) is observed besides liberated phos-
phane. In order to further clarify the role of water in those
reactions, an excess of D2O was added via syringe in one
attempt. This excess of water led to the separation of a colorless
oil from the reaction solution that contained iridium carbonate
species and overall to the formation of a more complicated
product mixture. However, [mer-cis-IrCl2(D)(Me2PhP)3] (60)
Figure 6. Molecular structure of the cationic complex of 9. Only
the most abundant part of the disordered atoms has been
represented (50% probability level; organic hydrogens have
been omitted for clarity) (top). Graphical representation of the
molecular disorder model of the cationic complex of 9 (bottom).
Selected bond distances (A): Ir-I(1) 2.8081(6), Ir-P(1) 2.349(3)/
2.355(6), Ir-P(2) 2.383(2)/2.317(7), Ir-P(3) 2.366(3)/2.358(6),
Ir-P(4) 2.363(3)/2.422(8), Ir-H 1.67(6) (the two values repor-
ted for Ir-P distances concern the two moieties of the disor-
dered model established).
was identified as one of the major products in solution,
indicating that water is indeed the source of the hydride ligands
observed in 6 and 7.
If the compound [Ir(Me2PhP)4]I (3) was applied in the
reaction with CO2, the cationic complex [trans-IrH(I)-
(Me2PhP)4]I (9) was isolated from the reaction mixture in
acetone instead of a neutral compound, [Ir(H)I2(Me2PhP)3].
In contrast to the starting materials described above,
[Ir(Me2PhP)4]PF6 (4) is unreactive toward CO2 under the
applied reaction conditions. This varying reactivity is prob-
ably due to its lower solubility as well to its different behavior
in solution. While 2 and 3 are in equilibrium with a neutral
(31) McLoughlin, M. A.; Keder, N. L.; Harrison, W. T. A.; Flesher,
R. J.; Mayer, H. A.; Kaska, W. Inorg. Chem. 1999, 38, 3223–3227.
(32) Deeming, A. J.; Shaw, B. L. J. Chem. Soc. A 1968, 1887–1889.
(33) Deeming, A. J.; Shaw, B. L. J. Chem. Soc. A 1969, 443–446.
(34) Bowman, K.; Deeming, A. J.; Proud, G. P. J. Chem. Soc., Dalton
Trans. 1985, 857–860.

Article
Table 2. Selected Bond Lengths and Angles of 1T, I, and 5T
Organometallics, Vol. 29, No. 7, 2010 1647
bond
length [A]
angle
[deg]
1T
I
5T
1T
I
5T
Ir-Cl
2.470 2.467 2.556 P1-Ir-P2
2.339 2.396 2.395 P2-Ir-P3
2.244 2.282 2.320 P1-Ir-Cl
96.9 95.2 97.0
96.3 100.2 97.0
87.5 82.9 85.0
Ir-P1
Ir-P2
Ir-P3
2.350 2.393 2.395 P2-Ir-Cl 166.2 163.1 94.7
Ir-C1
Ir-O4
C1-O1
C1-O2
C2-O2
C2-O3
C2-O4
2.208 2.008 P3-Ir-Cl
2.121 P1-Ir-C1
1.226 1.218 P2-Ir-C1
1.229 1.389 P3-Ir-C1
1.420 P1-Ir-O4
1.209 P2-Ir-O4
1.302 P3-Ir-O4
C1-Ir-O4
82.6 81.9 85.0
92.9 94.3
87.1 91.8
89.3 94.2
83.8
171.1
83.8
94.27
173.5
C1-Ir-Cl
compound (1 or [IrI(Me2PhP)3], respectively) as mentioned
above, for 4 no sign of ligand dissociation was observed.
Therefore, it can be assumed that the cationic species them-
selves are not reactive toward CO2 at all or do not form
products that are stable enough to be detected.
Finally, the obtained iridium carbonate 7 is of interest not
only due to the proposed role of such species in catalysis, e.g.,
the iridium-catalyzed alkylation of amines.35 It should be
noted that similar infrared data to those observed for 7 were
reported not only for other iridium carbonate compounds as
mentioned above but also for several metal complexes bear-
ing η2-coordinated CO2. Our results indicate that the assign-
ment of such complexes on the basis of their infrared data is
uncertain. Therefore, in the absence of structural data for
these compounds, neither carbonate compounds nor oxa-
late-containing complexes can be completely ruled out.1c
Theoretical Studies
In order to estimate the relative energy of compounds such
as 5 compared to the iridium(I) starting compound and
to gain further insight into the formation of 5 from 1 and
CO2, we performed DFT calculations for the related Me3P
complexes [IrCl(Me3P)3] (1T) and [mer-IrCl(C2O4-κ2C,O)-
(Me3P)3] (5T) using the unrestricted B3LYP functional and a
6-31* basis set to save processor time (for computational
details see the Experimental Section). The optimized struc-
tures of 1T and 5T fit well with the observed geometries. The
most significant bond lengths and angles are summarized in
Table 2.
In the next step the interaction of 1T with one molecule of
CO2 was investigated by calculations with different starting
geometries considering the different coordination modes of
CO2. The only local minimum geometry observed that shows
an interaction between the CO2 molecule and the iridium
center is shown in Figure 7.
Figure 7. Calculated structures of 1T (top), I (middle), and 5T
(bottom). H atoms are omitted for clarity.
Mulliken charge of -0.809 in 1T. The resulting metallacar-
boxylate structure is similar to known iridium and rhodium
CO2 complexes.3,40 The former carbon dioxide shows an
O1-C1-O2 bond angle of 137.7°, indicating an allyl-like
bonding situation that also corresponds to the highly nega-
tive Mulliken charge at iridium (-1.02). In comparison
with the octahedral rhodium compound [RhCl(η1-CO2)-
(diars)2],40 this angle is about 12° larger in pentacoordinated
I, reflecting the lower donor properties of the iridium frag-
ment. The chloro ligand is bent out of the IrP3 plane with a
distance of 0.67 A, while the iridium carbon bond is in an
almost perfect rectangular arrangement with respect to the
IrP3 plane. All iridium phosphorus distances show enlarged
bond lengths compared to [IrCl(Me3P)3], whereas the dis-
tance toward the chloro ligand remains essentially the same.
When a second CO2 molecule is allowed to approach I,
compound 5T was formed after optimization. In this struc-
ture the central iridium atom shows a slightly distorted
In this possible intermediate I of the formation of 5T the
iridium center is in a square-pyramidal coordination sphere
with CO2 coordinated in η1 fashion via carbon on top. Its
formation can be understood as an electrophilic attack of the
carbon atom of CO2 at the iridium center with its negative
(35) Balcells, D.; Nova, A.; Clot, E.; Gnanamgari, D.; Crabtree,
R. H.; Eisenstein, O. Organometallics 2008, 27, 2529–2535.
(36) Siegl, W. O.; Lapporte, S. J.; Collman, J. P. Inorg. Chem. 1971,
10, 2158–2165.
(37) Aresta, M.; Nobile, C. F. Inorg. Chim. Acta 1977, 24, L49–L50.
(38) Sakamoto, M.; Shimizu, I.; Yamamoto, A. Organometallics
1994, 13, 407–409.
(39) Aresta, M.; Nobile, C. F. J. Chem. Soc., Dalton Trans. 1977, 708–
711.
(40) Calabrese, J. C.; Herskovitz, T.; Kinney, J. B. J. Am. Chem. Soc.
1983, 105, 5914–5915.

1648 Organometallics, Vol. 29, No. 7, 2010
Langer et al.
Figure 8. HOMOs and LUMOs of 1T, I, and 5T.
octahedral coordination mode. The chloro ligand now is in a
cis-position with respect to C1 of the first carbon dioxide
ligand as well as to O4 of the second carbon dioxide ligand.
The three phosphane ligands are bonded in a meridional
fashion. Bond lengths of iridium toward P1 and P2 remain
unchanged with respect to [Ir(PMe3)3Cl(CO2)]. The corre-
sponding bond to P3 is enlarged due to the fact that now O4
is bonded in trans-position compared to Cl in [Ir(PMe3)3-
Cl(CO2)]. The carbon iridium bond is dramatically shor-
tened upon coordination of the second carbon dioxide ligand
in combination with the chloro ligand now being situated
trans to C1. Bond lengths in the carbon dioxide dimer are
indicative of isolated single and double bonds. All bond
angles are close to 120°. Figure 8 shows the HOMOs and
LUMOs of 1T, 5T, and I.
Scheme 7
The coordination and dimerization of two carbon dioxide
moieties at iridium is split into two elementary steps, which
are shown in Scheme 7. The first reaction step is slightly
endergonic, with a Gibbs free energy of þ21.06 kJ/mol,
whereas the second elementary step is marginally exergonic,
with a Gibbs free energy of -5.58 kJ/mol. Overall this results
in a slightly endergonic Gibbs free energy of þ15.48 kJ/mol
for the complete reaction, which is nevertheless low enough
to be overcompensated, e.g., by solubility effects.
However, transition states were not found for the forma-
tion of I or the formation of 5T from I. Therefore the acti-
vation energies of those processes remain unknown. While
these calculations suggest a stepwise uptake of two CO2 mole-
cules as postulated by Herskovitz,2 we were not able to detect
a species like I directly via NMR measurements.
shows a large deviation of the calculated shift of the metal-
bound carbon atom C1 (calcd δ = 206.2). This is related to
the fact that use of Stuttgart/Dresden effective core poten-
tials for iridium, taking into account relativistic effects, is not
applicable in calculations of NMR properties. Therefore
considerable variations of chemical shifts especially for those
atoms that are directly bonded to the respective metal atom
are commonly observed. In contrast, the chemical shift of C2
of δ =154.5 fits well with the observed value.
Conclusion
The reaction of [IrCl(Me2PhP)3] (1) with two equivalents
of CO2 leads to the iridacyclic compound 5, which is a rare
example of a structurally characterized metal compound,
containing this metallacyclic moiety. For the first time, NMR
data of such a compound are available. Since the forma-
tion of 5 is reversible, this type of iridium(III) compound is
In order to further connect the theoretical with the ex-
perimental results, we calculated the 13C NMR shifts of 5T.
A comparison of the calculated values with the ones observed
for the metallacyclic moiety of 5 (C1 δ=159.3; C2 δ=158.3)

Article
Organometallics, Vol. 29, No. 7, 2010 1649
potentially useful as a protected synthon of irdium(I) phos-
phane complexes with CO2 as the protective group. The
applicability is limited by the high moisture sensitivity of the
released iridium(I) complex in the presence of CO2, leading
to the formation of [IrCl2(H)(Me2PhP)3] (6) and [Ir(CO3)-
(H)(Me2PhP)3] (7), if trace amounts of water are present.
Quantum chemical calculations indicate that the forma-
tion of iridacycles like 5 is a two-step process. Initially, an
iridacarboxylate is formed from the iridium(I) starting ma-
terial and one molecule of CO2. This type of intermediate can
be stabilized with strongly basic chelating ligands as known
from literature. If such ligands are absent, the intermediate
reacts with an additional CO2 molecule to form the irida-
cycle.
7.1-7.3 (m, 2.5H, Ph toluene), 7.47 (m, 4H, p-CH Ph), 7.54 (t,
J = 7.3 Hz, 8H, CH Ph), 7.80 (m, 8H, CH Ph). 13C{1H} NMR
(100.6 MHz, d6-acetone): δ 17.8 (br, 8 ꢀ CH3), 21.5 (s, CH3
toluene), 126.1 (s, p-CH toluene), 129.1 (s, m-CH toluene), 129.3
(br, 8ꢀCH Ph), 129.8 (s, o-CH toluene), 130.8 (s, 4ꢀp-CH Ph),
131.6 (br, 8ꢀCH Ph), 138.5 (s, i-C toluene), 140.6 (br, 4ꢀC Ph).
31P{H} NMR (162 MHz, d6-acetone): δ -15.6 (s).
[Ir(Me2PhP)4]I (3). Light was excluded during the reaction by
wrapping the apparatus in aluminum foil. Brown [IrI(coe)2]2
(187 mg, 0.173 mmol) was suspended in diethyl ether (9 mL).
Me2PhP (0.20 mL, 1.41 mmol) was added dropwise to the dark
brown suspension with rapid stirring. A pale yellow precipitate,
which initially formed during the addition, redissolved and an
orange-colored precipitate occurred. The orange-brown suspen-
sion was stirred for an additional 30 min after the addition of the
phosphane was complete. Afterward the solid was isolated by
filtration, washed with hexane (3 ꢀ 4 mL), and dried in a
vacuum. Yield: 255 mg (84%). 1H NMR (400 MHz, d6-acetone):
δ 1.39 (q, J=1.4 Hz, 24H, CH3), 7.48 (m, J=7.3 Hz, 4H, p-CH
Ph), 7.55 (t, J = 7.3 Hz, 8H, CH Ph), 7.80 (m, 8H, CH Ph).
Experimental Section
General Comments. All reactions were carried out under
argon using standard Schlenk techniques, if not otherwise
stated. Prior to use, thf, toluene, diethyl ether, and hexane were
dried and deoxygenated with an Innovative Technology Solvent
Purification System. Acetone was dried over CaH2 and distilled
under argon prior to use. Dimethoxyethane was dried over
potassium hydroxide and distilled over Na/benzophenone. In-
frared spectra were recorded using a Perkin-Elmer Spectrum
One spectrometer. Carbon and hydrogen analyses were per-
formed with a Perkin-Elmer 2400 microanalyzer. 1H, 13C{1H},
and 31P{1H} NMR spectra were recorded on a Bruker Avance
400, 300, or 200 MHz spectrometer. Chemical shifts are reported
in parts per million and referenced to SiMe4 using the residual
signal of the deuterated solvent as reference and 85% phospho-
ric acid, respectively. [IrCl(coe)2]2 was prepared according
to the literature.41 [IrI(coe)2]2 was prepared in analogy with
[IrI(cod)]2.42 The crude impure product obtained was used
without further purification.
13C{1H} NMR (75.5 MHz, d6-acetone): δ 18.0 (q, JC-P
=
9.8 Hz, 8 ꢀ CH3), 129.3 (br, q, JC-P = 1.9 Hz, 8 ꢀ CH Ph),
130.8 (s, 4ꢀp-CH Ph), 131.6 (br, q, JC-P=2.7 Hz, 8ꢀCH Ph),
140.5 (br, q, JC-P=∼15 Hz, 4ꢀC Ph). 31P{H} NMR (162 MHz,
d6-acetone): δ -15.6 (s).
[Ir(Me2PhP)4]PF6 (4). Pure Me2PhP (0.22 mL, 1.55 mmol)
was added dropwise to a stirred suspension of [IrCl(coe)2]2 (159mg,
0.18 mmol) in methanol (4 mL). The immediately formed red
solution was stirred for an additional 5 min. Afterward a
solution of NH4PF6 (120 mg, 0.74 mmol) in 2 mL of methanol
was added, and rapid crystallization of the product occurred.
After standing for 3 h at room temperature, the supernatant
solution was decanted, and the remaining red solid was washed
with cold methanol (2 ꢀ 5 mL) and ether (5 mL) and dried
in a vacuum. Yield: 206 mg (65%). 31P{H} NMR (162 MHz,
d6-acetone): δ -15.5(s).
Reaction of 1 with CO2 (typical procedure). [IrCl(Me2PhP)3]
(1) (100 mg, 0.156 mmol) was dissolved in toluene (10 mL). The
resulting orange solution was pressurized with CO2 (0.6 bar) and
stirred at room temperature for 3 days. The color of the reaction
mixture faded during this time to pale yellow, and a cloudy
precipitate formed. The precipitate was removed by filtration,
and the clear solution was reduced to dryness in a vacuum. The
oily residue was stirred with hexane (10 mL) until all oil had
transformed into a white solid. Afterward the supernatant
solution was decanted. The remaining solid was washed with
diethyl ether (5 mL) and hexane (3 ꢀ5 mL) and then dried in a
vacuum. Yield: 81 mg (mixture 6-8).
[IrCl(Me2PhP)3] (1). Pure Me2PhP (0.33 mL, 2.32 mmol) was
added dropwise at 0 °C to a stirred suspension of orange
[IrCl(coe)2]2 (346 mg, 0.39 mmol) in ether (10 mL). While the
starting material dissolved, a yellow microcrystalline precipitate
formed. The stirring was continued for 30 min and then the
precipitate was isolated by filtration over a Schlenk frit, washed
with cold diethyl ether (5 mL) and hexane (2ꢀ10 mL), and dried
in a vacuum. Yield: 333 mg (67%). Suitable crystals for X-ray
diffraction were obtained by cooling a saturated solution of 1 in
diethyl ether from room temperature to 0 °C. Anal. Calcd for
C24H33P3IrCl: C 44.89, H 5.18. Found: 44.78, H 5.21. 1H NMR
(400 MHz, d6-benzene): δ 1.13 (d, J=8.4 Hz, 6H, CH3), 1.68 (t,
J = 3.2 Hz, 12H, CH3), 6.95-7.05 (m, 6H, Ph), 7.64-7.71 (m,
9H, Ph). 13C{1H} NMR (50.3 MHz, d8-thf): δ 16.2 (t, J=17.4 Hz,
4 ꢀ CH3), 20.5 (d, J = 36.9 Hz, 2 ꢀ CH3), 128.0 (d, J = 9.8 Hz,
2 ꢀ o-CH Ph), 128.3 (t, J = 4.5 Hz, 4 ꢀ o-CH Ph), 129.4 (s, 3 ꢀ
p-CH Ph), 132.2 (d, J ≈ 11 Hz, 2ꢀm-CH Ph), 132.3 (t, J=5.9 Hz,
4 ꢀ m-CH Ph), 141.2 (t, J = 21.6 Hz, 2 ꢀ i-C Ph), 142.3 (d, J =
51.0 Hz, i-C Ph). 31P NMR (162 MHz, d6-benzene): δ -7.1 (d,
J =25.3 Hz, 2P), -23.2 (t, J =25.3 Hz, 1P).
[mer-IrCl(C2O4-K2C,O)(Me2PhP)3] (5). [IrCl(Me2PhP)3] (1)
(59 mg, 0.092 mmol) was dissolved in toluene (1.5 mL) and
additionally dried over Na/benzophenone. The resulting orange-
colored solution was pressurized with CO2 (0.4 bar) and stirred
for 10 min at room temperature. Afterward it was stored over-
night at -40 °C, resulting in the formation of white crystals. The
supernatant solution was decanted, and the remaining solid was
dried in a vacuum. Yield: 54.5 mg (81%). In some attempts no
crystallization occurred due to oversaturation of the solution. In
these cases, the Schlenk tube was shaken to initiate crystal-
lization and stored again at -40 °C. Anal. Calcd for C26H33ClIr-
O4P3 (730.128): C 42.77, H 4.56. Found: C 42.71, H 4.53. NMR
data were extracted from the NMR data of the reaction mixture,
consisting of 1, 5, 6, and 7 as main components. 1H NMR (400
MHz, d6-benzene): δ 1.24 (d, J=10.8 Hz, 6H, CH3), 1.50 (t, J=
3.6 Hz, 6H, CH3), 1.71 (t, J=4.0 Hz, 6H, CH3), 6.95-7.05 (m,
6H, Ph), 7.64-7.71 (m, 9H, Ph). 13C{1H} NMR (50.3 MHz, d8-
thf): δ 11.6 (t, J = 18.3 Hz, 2 ꢀ CH3), 11.9 (t, J = 20.4 Hz, 2 ꢀ
CH3), 14.4 (d, J=42.1 Hz, 2ꢀCH3), 134.5 (t, J=26.7 Hz, 2ꢀi-C
Ph), 136.3 (dt, J = 59.1 Hz, J = 3.8 Hz, i-C Ph), 158.3 (d,
J = 3.0 Hz, -O-C(O)-O), 159.3 (pseudo-q, J = 6.4 Hz,
Ir-C). (All other signals of the phenyl groups cannot be
[Ir(Me2PhP)4]Cl 0.5toluene (2). Pure Me2PhP (0.36 mL, 2.53
3
mmol) was added dropwise to a stirred suspension of [IrCl-
(coe)2]2 (256 mg, 0.29 mmol) in toluene (6 mL). The resulting red
solution was stored overnight at 4 °C. Afterward the mother
liquor was decanted from the formed red crystals and the
crystals were washed with toluene (2 ꢀ 5 mL) and dried in a
vacuum. Yield: 394 mg (83%). Anal. Calcd for C35.5H48P4IrCl:
C 51.60, H 5.86. Found: 51.78, H 5.90. 1H NMR (400 MHz, d6-
acetone): δ 1.39 (s, br, 24H, CH3), 2.30 (s, 1.5H, CH3 toluene),
(41) Van der Ent, A.; Onderdelinden, A. L. Inorg. Synth. 1990, 28, 90–
92.
(42) Yamagata, T.; Nagata, M.; Mashima, K.; Tani, K. Acta Crystal-
logr. 2007, E63, m2402.

1650 Organometallics, Vol. 29, No. 7, 2010
Langer et al.
assigned unambiguously.) 31P{1H} NMR (162 MHz, d6-ben-
zene): δ -31.3 (d, J= 18.3 Hz, 2P), -41.0 (t, J= 18.3 Hz, 1P).
Suitable crystals for X-ray diffraction were obtained from the
reaction of 1 with CO2 in DME at room temperature.
to stand for an hour. Afterward the formed crystals were
isolated by decantation, washed with hexane (5 mL), and dried
in a vacuum. A yield was not determined.
Suitable crystals of the composition 9 acetone for X-ray
diffraction were obtained by recrystallization from acetone.
3
[mer-IrCl2(H)(Me2PhP)3] (6). [IrCl(Me2PhP)3] (520 mg, 0.81
mmol) was dissolved in toluene (25 mL), and gaseous HCl was
slowly bubbled through the initially orange-yellow solution.
The color changed rapidly to pale yellow. When no further
lightening was observed, the HCl stream was stopped and a
stream of argon was bubbled through the solution for 30 min to
remove the excess HCl. Then the solution was reduced to
dryness under reduced pressure, and hexane (20 mL) was added.
The resulting suspension was stirred for 20 min, and the super-
natant solution was decanted afterward. The remaining white
solid was washed with hexane (3 ꢀ5 mL) and dried in vacuum.
Yield: 523 mg (95%). 1H NMR (400 MHz, d6-benzene): δ
1
IR: νIr-H 2180 (w). H NMR (300 MHz, d6-acetone): δ -16.74
(q, J=12.3 Hz, 1H, Ir-H), 2.07 (s, br, 24H, CH3), 7.3-7.5 (m,
12H, CH Ph), 8.03 (m, 8H, CH Ph). 31P{H} NMR (121 MHz, d6-
acetone): δ -42.2 (br). 13C{1H} NMR (75.5 MHz, d6-acetone):
δ = 21.2 (m, br, 8 ꢀ CH3), 129.3 (br, 8 ꢀ CH Ph), 131.5 (s, 4 ꢀ
p-CH Ph), 133.5 (br, 8ꢀCH Ph). The signals for the ipso-carbon
atoms were not observed.
Quantum Chemical Calculations. Ab initio calculations of
carbon dioxide, [IrCl(Me3P)3], [IrCl(CO2)(Me3P)3], and [IrCl-
(C2O4)(Me3P)3] have been performed using the DFT approach
as implemented in GAUSSIAN03.43 For our calculations we
chose the unrestricted B3LYP functional and a 6-31* basis set.
Treatment of iridium was realized by taking into account
relativistic effects using the Stuttgart-Dresden pseudopoten-
tials as implemented in GAUSSIAN03. No symmetry con-
straints whatsoever have been considered. In order to save
computational time, trimethylphosphane was used instead of
the aromatic derivative. All structures were fully optimized, and
additional frequency calculations were performed. There are no
imaginary frequencies in the calculations of all theoretically
investigated compounds, meaning that the reported structures
are truly minimum structures on the hypersurface. For the
calculation of reaction enthalpies zero-point corrections as well
as corrections corresponding to entropy effects were considered.
X-ray Structure Determination of 1, 2, 5, and 9. X-ray diffrac-
tion data for 1, 2, and 9 were recorded at 100(2) K on a Bruker-
AXS Smart CCD diffractometer, using a ω scan technique with
2
2
-20.56 (dt, J = 19.2 Hz, J = 11.6, 1H, Ir-H), 1.14 (d, J =
10.0 Hz, 6H, CH3), 1.92 (t, J = 4.0 Hz, 6H, CH3), 2.02 (t, J =
4.0 Hz, 6H, CH3), 6.6-7.1 (m, 11H, Ph), 7.6-7.8 (m, 4H, Ph).
13C{1H} NMR (75.5 MHz, CD2Cl2): δ 13.3 (t, J=19.7 Hz, 2ꢀ
CH3), 15.7 (t, J =19.6 Hz, 2 ꢀCH3), 17.6(dt, J = 39.9 Hz, J =
2.3 Hz, 2ꢀCH3), 128.4 (d, J=10.1 Hz, 2ꢀm-CH Ph), 128.8 (t,
J = 4.6 Hz, 4 ꢀm-CH Ph), 129.5 (d, J = 9.4 Hz, 2 ꢀo-CH Ph),
129.6 (s, p-CH Ph), 129.9 (s, ꢀ p-CH Ph), 130.9 (t, J = 5.1 Hz,
4ꢀo-CH Ph), 137.5 (dt, J=60.6 Hz, J=4.3 Hz, i-C Ph), 137.7
(dt, J = 1.0 Hz, J = 24.2 Hz, 2 ꢀ i-C Ph). 31P{1H} NMR (162
MHz, d6-benzene): δ -27.9 (t, J = 19.6 Hz, 1P), -29.9 (d, J =
19.6 Hz, 2P).
[mer-Ir(CO3)(H)(Me2PhP)3] (7). Ag2CO3 (250 mg, 0.90 mmol)
was added to a solution of [mer-IrCl2(H)(Me2PhP)3] (100 mg,
0.147 mmol) in acetone (5 mL). The resulting suspension was
stirred for 24 h with exclusion of light. Afterward the solid was
filtered off and the clear pale yellow solution was reduced to
dryness. Hexane (10 mL) was added to the remaining oil, and
the mixture was stirred for 30 min. The formed off-white solid was
isolated by decantation and washed with hexane (2ꢀ5 mL). Yield:
87 mg (crude product). The isolated solid consisted of 7 (80%)
besides three impurities (20%), as judged by 31P NMR measure-
ments. 1H NMR (400 MHz, d6-benzene): δ -21.89 (dt, 2J =
21.6 Hz, 2J=15.6 Hz, 1H, Ir-H), 0.83 (d, J=10.4 Hz, 6H, CH3),
1.48 (t, J = 3.6 Hz, 6H, CH3), 1.70 (t, J = 4.0 Hz, 6H, CH3),
7.10-7.4 (m, 11H, Ph), 7.4-7.55 (m, 4H, Ph). 13C NMR (100
ꢀ
Mo KR radiation (λ=0.71073 A). All structures were solved by
direct methods (SHELXS)44 and refined on F2 by full-matrix
least-squares techniques using the SHELXL-97 program.45
Non-hydrogen atoms were refined with anisotropic displace-
ment parameters, and most hydrogens were refined riding on
their parent atoms.
A disordered toluene molecule was found in the electron-
density map of compound 2. The atoms of the disordered
solvent molecule were refined anisotropically, but their hydro-
gen atoms have not been included in the model.
After isotropic refinement of compound 9, two disordered
sets of four phosphanes were evident from the difference Fourier
map. A model of disorder has been established, allowing the two
sets complementary occupancy factors, each phosphane sharing
a methyl group with the adjacent disordered moiety (Figure 8).
The second methyl and the phenyl groups have been determined
from the residual map and refined isotropically. The four phenyl
groups of the less abundant disordered set have been constrained
MHz, d8-thf): δ 8.3 (t, 1JP-C=16.2 Hz, 2ꢀCH3), 16.7 (t, 1JP-C
=
19.9 Hz, 2 ꢀ CH3), 19.1 (d, 1JP-C = 39.1 Hz, 2 ꢀ CH3), 128.9 (d,
3JP-C=10.0 Hz, 2ꢀm-CH Ph), 129.2 (t, 3JP-C=4.2Hz, 4ꢀm-CH
Ph), 130.4 (s, p-CH Ph), 130.6 (s, 2ꢀp-CH Ph), 131.2 (d, 2JP-C
=
10.1 Hz, 2 ꢀ o-CH Ph), 131.6 (t, 2JP-C = 10.1 Hz, 4 ꢀ o-CH Ph),
136.9 (t, 1JP-C =25.5 Hz, 2ꢀi-C Ph), 138.8 (d, 1JP-C =56.1 Hz,
3
i-C Ph), 169.2 (d, JP-C = 3.2 Hz, CO32-). 31P{1H} NMR
(162 MHz, d6-benzene): δ -13.4 (d, J = 16.8 Hz, 2P), -38.4 (t,
J=16.8 Hz, 2P).
“[mer-IrCl(CO3)(Me2PhP)3]” (8). This compound was obser-
ved as a minor byproduct in the reaction of 1 with CO2 and
water. 8 was not isolated and was characterized only by NMR in
a mixture with 6 and 7. 1H NMR (400 MHz, d6-benzene): δ 0.94
(d, J=10.4 Hz, 6H, CH3), 1.40 (t, J=3.6 Hz, 6H, CH3), 1.88 (t,
J = 4.0 Hz, 6H, CH3), 6.85-7.9 (several m, 15H, Ph). 31P{1H}
NMR (162 MHz, d6-benzene): δ -28.1 (d, J = 16.8 Hz, 2P),
-42.2 (t, J = 16.8 Hz, 2P).
[trans-Ir(H)(I)(Me2PhP)4]I (9). A sample of [Ir(Me2PhP)4]I
(3) was dissolved in 2 mL of acetone (2 mL). The resulting red
solution was pressurized with CO2 (0.4 bar) and stirred for
15 min at room temperature. Afterward the solution was stored
at -40 °C for 5 days. A small amount of a colorless, amorphous
precipitate formed during this time, and the solution bleached to
pale yellow. Then the supernatant solution was rapidly decanted
under argon, resulting in an immediate color change back to red.
Now, the solution was slowly concentrated in a vacuum at room
temperature until small colorless crystals started to form. Eva-
poration and stirring was stopped, and the solution was allowed
(43) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, R. J.; Montgomery, J. A., Jr.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson,
G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai,
H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken,
V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev,
O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, D. A.; Strain, M. C.; Farkas,
O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.;
Gonzalez, C. Pople, J. A. Gaussian 03, Revision D.01; Gaussian, Inc.:
Wallingford, CT, 2004.
(44) Sheldrick, G. M. SHELXS-97 Program for Crystal Structure
€
Solution; University of Gottingen: Germany, 1997.
(45) Sheldrick, G. M. SHELXL-97 Program for Crystal Structure
€
Refinement; University of Gottingen: Germany, 1997.

Article
Organometallics, Vol. 29, No. 7, 2010 1651
Table 3. Crystal Data and Refinement Details for the X-ray Structure Determinations
1
2
5
9
formula
fw (g mol-1
T/°C
cryst syst
space group
a/A
C
642.12
-173(2)
triclinic
P1
9.8452(8)
11.7899(10)
12.8026(11)
63.7240(10)
83.5420(10)
66.0080(10)
1213.23(18)
2
1.758
58.2
15 071
5425
5746/0.0249
0.0610
0.0239
24H33ClIrP3
C32H44ClIrP4 0.5 C7H8
C26H33ClIrO4P3
730.08
-90(2)
monoclinic
P21/n
9.8246(4)
12.7951(4)
22.0739(9)
90.00
96.089(2)
90.00
2759.18(18)
4
1.758
51.4
18 150
5012
C32H45I2IrP4 0.5C3H6O
3
3
)
1652.67
-173(2)
monoclinic
P21/n
9.8930(10)
28.719(3)
12.5426(13)
90.00
91.906(2)
90.00
3561.5(6)
2
1.627
40.32
22 290
6379
7710/0.0475
0.0944
0.0462
1028.60
-173(2)
monoclinic
P21/c
11.8106(16)
17.318(2)
18.393(2)
90.00
92.198(3)
90.00
3759.4(9)
4
1.817
53.87
23 569
6425
8300/0.0397
0.1091
0.0452
3
b/A
c/A
R/deg
β/deg
γ/deg
V/A3
Z
F/g cm-3
3
μ/cm-1
measd data
data with I > 2σ(I)
unique data/Rint
wR2 (all data, on F2)a
R1 (I > 2σ(I))a
sb
6202/0.0470
0.0706
0.0344
1.093
1.134
1.031
1.040
res dens/e A-3
2.269/-0.418
multiscan
0.30/0.62
746438
1.633/-2.226
multiscan
0.4994/0.9024
746439
P
1.101/-1.355
multiscan
0.523/0.680
746440
1.314/-0.974
multiscan
0.433/0.633
746441
3
absorpt method
absorpt corr Tmin/max
CCDC No.
P
P
P
P
a Definition of the R indices: R1 = ( ||Fo|-|Fc||)/ |Fo|. wR2 = { [w(Fo2 - Fc2)2]/ [w(Fo2)2]}1/2 with w-1 = σ2(Fo2) þ (aP)2. b s = { [w(Fo
-
2
Fc2)2]/(No - Np)}1/2
.
as rigid groups. Anisotropic displacement parameters were used
only for the nondisordered atoms (Ir and I), the phosphorus
atoms, and the shared methyl groups. At this stage of refine-
ment, clear evidence of the presence of highly disordered solvent
(acetone) was obtained. Several trials to model this disorder
were unfruitful, giving rise to abnormal geometries. An analysis
of the solvent region has been performed using the SQUEEZE
program.46 The contribution of the observed contents to the
total structure factor has been calculated and incorporated in
the further least-squares refinement of the main residues. Only
hydrogens for the more abundant disordered methyl groups
have been considered. The hydride ligand was included from
electrostatic potential calculation (HYDEX program)47 and
allowed to refine as a free isotropic atom.
tion. Data were corrected for Lorentz, polarization, and absorp-
tion effects.48-50 The structure was solved by direct methods
(SHELXS)44 and refined by full-matrix least-squares techniques
against Fo2 (SHELXL-97).45
Acknowledgment. This work was funded by MEC
(Grants CTQ2006-01629 and CONSOLIDER INGENIO-
2010 CSD2006-0015) and the Deutsche Forschungsge-
meinschaft (DFG) with grants to J.L. (LA 2474/1-1 and
LA 2474/1-2).
Supporting Information Available: CIF files giving data
collection and refinement details as well as positional coordi-
nates of all atoms. This material is available free of charge via the
Internet at http://pubs.acs.org. In addition, crystallographic
data (excluding structure factors) has also been deposited with
the Cambridge Crystallographic Data Centre as supplementary
publications CCDC-746438 for 1, -746439 for 2, -746440 for 5,
and -746441 for 9. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK [e-mail: deposit@ccdc.cam.ac.uk].
Intensity data of 5 were collected on a Nonius Kappa CCD
diffractometer using graphite-monochromated Mo KR radia-
(46) der Luis, P. V.; Spek, A. L. Acta Crystallogr. 1990, A46, 194–201.
(47) Orpen, A. G. J. Chem. Soc., Dalton Trans. 1980, 2509–2516.
(48) COLLECT, Data Collection Software; Nonius B.V.: The Nether-
lands, 1998.
(49) Otwinowski, Z; Minor, W. Processing of X-Ray Diffraction
Data Collected in Oscillation Mode. In Methods in Enzymology; Carter,
C. W., Sweet, R. M., Eds.; Academic Press: New York, 1997; Vol. 276, Part
A, pp 307-326.
(50) SORTAV. Blessing, H. R. J. Appl. Crystallogr. 1997, 30,
421-426.