Synthesis and characterization of new pentamethylcyclopentadienyl iridium hydride complexes

Article abstract of DOI:10.1016/j.jorganchem.2012.05.049

Pentamethylcyclopentadienyl iridium dihydride complexes [Cp*Ir(H)₂(PR₃)]; (PR₃ = PPh ₂Me, PTA) were prepared by reaction of [Cp*IrCl ₂(PPh₂Me)] and [Cp*IrCl₂(PTA)], respectively,

Full text of DOI:10.1016/j.jorganchem.2012.05.049

Journal of Organometallic Chemistry 715 (2012) 113e118
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of new pentamethylcyclopentadienyl iridium
hydride complexes
*
*
María Talavera, Sandra Bolaño , Jorge Bravo , Jesús Castro, Soledad García-Fontán
Departamento de Química Inorgánica, Universidade de Vigo, Facultade de Química, Edificio de Ciencias Experimentales, 36310 Vigo, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Pentamethylcyclopentadienyl iridium dihydride complexes [Cp*Ir(H)2(PR3)]; (PR3 ¼ PPh2Me, PTA) were
prepared by reaction of [Cp*IrCl2(PPh2Me)] and [Cp*IrCl2(PTA)], respectively, with an excess of sodium
bis(2-methoxyethoxy)aluminium hydride (Red-Al). Protonation of the dihydride [Cp*Ir(H)2(PPh2Me)]
with HBF4$Et2O at low temperature gave the classical trihydride complex [Cp*Ir(H)3(PPh2Me)]BF4 that
displays quantum mechanical exchange coupling. Reaction of [Cp*IrCl2(PPh2Me)] with CO gave the half-
sandwich iridium carbonyl compound [Cp*IrCl(CO)(PPh2Me)]Cl which, by reaction with NaBPh4, yielded
yellow microcrystals of [Cp*IrCl(PPh2Me)(CO)]BPh4 adequate for X-ray diffraction analysis.
Ó 2012 Elsevier B.V. All rights reserved.
Received 7 February 2012
Received in revised form
24 May 2012
Accepted 31 May 2012
Keywords:
Hydrides
Iridium
Half-sandwich complexes
Pentamethylcyclopentadienyl ligand
PTA
1. Introduction
to obtain the new half-sandwich iridium carbonyl compounds
[Cp*IrCl(CO)(PPh2Me)]A, A ¼ Cl (3); BPh4 (4). The X-ray structure of
Interest in the chemistry of hydrido transition metal complexes
is increasing in inorganic, biochemical and organometallic research
owing to their reactivity and applications in areas such as catalysis
and materials science, amongst others [1].
compound 4 was elucidated.
2. Results and discussion
The reactivity of these compounds is highly dependent on the
metal atom and the coligands that complete the coordination
sphere of the metal. Appropriate design of this environment allows
tuning both the steric and electronic properties of the resulting
compound. The presence of a Cp* ligand on di- and polyhydride
complexes will force hydride ligands to be in close contact,
favouring their interaction and the possibility to be eliminated as
H2 and creating a free coordination site which is very important in
metal catalysis [2]. On the other hand, di- and polyhydride
complexes can display exchange couplings which, besides relevant
theoretical aspects [3], may present applications as sensors of very
weak interactions in solution or as temperature probes in NMR [4].
We report here the synthesis and characterization of a set of
new half-sandwich iridium hydride complexes bearing the
PPh2Me phosphine or the water-soluble phosphine 1,3,5-triaza-7-
phosphaadamantane (PTA), and their protonation studies. Attempts
to characterize an unexpected carbonyl subproduct obtained in the
synthesis of the dihydride [Cp*Ir(H)2(PPh2Me)] (1) prompted us
2.1. Synthesis and characterization of the dihydrides
[Cp*Ir(H)2(PR3)] PR3 ¼ PPh2Me (1), PTA (2)
The dihydrides [Cp*Ir(H)2(PPh2Me)] (1) and [Cp*Ir(H)2(PTA)] (2)
[5] can be obtained by two different ways:
1) By reaction of toluene solutions of the chlorocomplexes
[Cp*IrCl2(PPh2Me)] and [Cp*IrCl2(PTA)], respectively, with an
excess of sodium bis(2-methoxyethoxy)aluminium hydride
(Red-Al) (Scheme 1);
2) By reaction of methanol solutions of the same chlorocomplexes
with NaOMe [6].
The second method gives better yields for complex 2 but in the
case of complex 1, the reaction of [Cp*IrCl2(PPh2Me)] with NaOMe
gives, besides to the dihydride compound 1 a non-identified
subproduct, that was detected by NMR and IR spectroscopies (see
below) but we were not able to isolate it because it easily decom-
poses during the workup of the mixture.
Compounds 1 and 2 were isolated as brown solids and are air-
unstable [7]. They were characterized byIR and NMR spectroscopies.
* Corresponding authors. Tel.: þ34 986812275; fax: þ34 986813798.
E-mail addresses: bgs@uvigo.es (S. Bolaño), jbravo@uvigo.es (J. Bravo).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.05.049

114
M. Talavera et al. / Journal of Organometallic Chemistry 715 (2012) 113e118
Bibliographic data [12] allows us to exclude the mono-
carbonylcompound [Cp*Ir(CO)(PPh2Me)] [1H (CD2Cl2):
d 7.6 (m,
10 H, C6H5), 1.82 (d, JPH ¼ 1.5 Hz, 15 H, Cp*) ppm; 31P{1H} (CDCl3):
d
¼ 25.18 (s) ppm], so we intended to synthesize the unknown
carbonyl compound trying different strategies. First, we have
refluxed a methanolic solution of the dihydride compound 1 to
produce the expected carbonylation reaction. Unfortunately we
have obtained a mixture of compounds that we were not able to
identify, but none of the signals observed in the 31P NMR spectrum
were coincident with that observed for the aforementioned
subproduct. In a second attempt we have reacted a methanolic
solution of the chlorocomplex [Cp*IrCl2(PPh2Me)] with CO(g) at
75 ꢁC under pressure, obtaining the Ir(III) carbonyl compound
[Cp*IrCl(CO)(PPh2Me)]Cl and its spectroscopic parameters were not
coincident with those of the subproduct either (see next para-
graph). To gather more experimental evidences about the nature of
this compound, we have treated a solution of the mixture of the
dihydride compound 1 and the unknown subproduct (in different
solvents as MeOH or CH2Cl2 and with similar results, which indi-
cates that the solvent does not play any important role in the
mixture behaviour) with NaBPh4 and also with NaPF6, to see if the
substitution of the counteranion helps the precipitation of the
compound. Results were somewhat unexpected: There is no
precipitation in any case but, when these reactions were monitored
by NMR spectroscopy we have observed, in all cases, the progres-
sive disappearance of the mixture 1H and 31P{1H} NMR signals and
the raising of new signals corresponding to the cationic hydride
carbonyl compound [Cp*IrH(CO)(PPh2Me)]þ, already reported in
the literature although with a different counteranion (CF3COOꢀ)
[12,13]. All these results do not allow us to undoubtedly propose
the structure of the unknown compound but we can assure the
presence of CO, Cp* and PMePh2 ligands bonded to the iridium
centre.
Scheme 1.
The IR spectra showsmedium absorptions at 2109 and 1922 cmꢀ1 for
compound 1, and strong absorptions at 2095 and 1896 cmꢀ1 for
compound 2, attributable to the
NMR spectrum shows a high field doublets at
n
(IreH) vibrations [8,9]. The 1H
d
ꢀ17.83 ppm
(2JHeP
¼
31.4 Hz) (compound 1), and at d
ꢀ17.91 ppm
(2JHeP ¼ 32.5 Hz) (compound 2), both integrating by two protons,
suggesting the presence of two hydride ligands coupled to the
phosphorus nucleus of the phosphane ligand.
However, to confirm this hypothesis, and to rule out other
possibilities, such as a dynamic cis dihydride or a dihydrogen
complex, we have carried out a variable temperature 400 MHz
study. The relaxation time, T1, of the hydride resonance in
complexes 1 and 2 was measured as a function of temperature using
a standard inversion recovery sequence. The minimum T1 of 459 ms
at 200 K for compound 1 and of 647 ms at 209 K for compound 2 was
estimated by plotting ln T1 vs 1000/T. Dihydrides and dihydrogen
complexes can be distinguished by their minimum T1 value by
following the method of Halpern and co-workers [10]. The T1
minimum values calculated for compounds 1 and 2 clearly indicate
their nature as classical dihydride complexes.
The 31P{1H} NMR spectrum of the complexes shows a singlet
at ꢀ5.57 ppm for compound 1 and at ꢀ68.29 ppm for compound 2;
and the 13C{1H} NMR spectrum displays, besides the signals corre-
spondent to the R groups of the phosphane ligand (see Experimental
part), signals at 10.9 ppm and 92.3 ppm (compound 1) and at
11.9 ppm and 92.3 ppm (compound 2) assigned to the Cp* ligand.
As it was previously mentioned, reaction of [Cp*IrCl2(PPh2Me)]
with NaOMe gives, besides to the dihydride compound 1 a non-
identified subproduct detected by NMR and IR spectroscopies.
Figs.1 and 2 show the 31P{1H} and 1H NMR spectra of the mixture. It
is remarkable the high similarity among the signals of both
compounds, except for the low frequency part of the 1H NMR
spectrum, in which only the signal corresponding to the hydride
nuclei of compound 1 is observed, indicating that the subproduct is
not a hydride complex. On the other hand, the IR spectrum of the
mixture shows a strong absorption at 1909 cmꢀ1 and its 13C{1H}
NMR spectrum displays a doublet at 182.7 ppm (JCeP ¼ 15.5 Hz).
These facts indicate the presence of an iridium complex with, at
least, carbonyl, Cp* and PMePh2 ligands on its structure [11].
2.2. Synthesis and characterization of the carbonyl complexes
[Cp*IrCl(CO)(PPh2Me)]A, A ¼ Cl (3); BPh4 (4)
Compound [Cp*IrCl(CO)(PPh2Me)]Cl (3) was prepared by treat-
ing a methanolic solution of the chlorocomplex [Cp*IrCl2(PPh2Me)]
with CO(g) at 75 ꢁC under pressure (Scheme 2). A yellow solid was
obtained and characterized by IR and NMR spectroscopies. The IR
spectrum shows a strong band at 2042 cmꢀ1 attributable to the nCO
band. The 31P{1H} NMR spectrum displays a singlet at ꢀ12.26 ppm
corresponding to the phosphorus nuclei of the phosphine ligand
and the 13C{1H} NMR spectrum shows, apart from the signals cor-
responding to the Cp* and PPh2Me ligands, a low field doublet
(d
¼ 166.1 ppm; 2JCeP ¼ 14.3 Hz) assignable to the carbonyl ligand.
Treating a methanol solution of this complex with NaBPh4
yielded yellow microcrystals of [Cp*IrCl(PPh2Me)(CO)]BPh4 (4)
adequate for X-ray diffraction analysis.
Fig. 1. 31P{1H} NMR spectrum of the mixture of compound 1 and the unknown subproduct (*) obtained by reaction of [Cp*IrCl2(PPh2Me)] with NaOMe.

M. Talavera et al. / Journal of Organometallic Chemistry 715 (2012) 113e118
115
Fig. 2. 1H NMR spectrum of the mixture of compound 1 and the unknown subproduct (*) obtained by reaction of [Cp*IrCl2(PPh2Me)] with NaOMe.
AnORTEPviewofthis complexisshowninFig. 3 togetherwiththe
labelling scheme while selected bond distances and angles are listed
in Table 1. The structure of the complex consists of a tetraphenyl
borateanion(notrepresentedinthefigure)anda cation formedbyan
compound 1 the protonation reaction gave the trihydride complex
[Cp*IrH3(PPh2Me)]BF4 (5) as a brown solid that immediately
precipitated (Scheme 3).
The spectral parameters of complex 5 show that the protonation
site is the metal centre and not a hydride ligand. This reaction can
be reverted by adding Et3N. The 1H NMR spectrum of the complex 5
displays a doublet resonance at ꢀ13.01 ppm, integrating by three
protons with a coupling constant 2JHeP ¼ 9.2 Hz. The 31P{1H} NMR
spectrum shows a singlet at ꢀ8.30 ppm, corresponding to the
phosphorous nucleus of the phosphine ligand. A variable temper-
ature 1H NMR study shows that the spectra are temperature
dependent. The presence of a single resonance at 298 K that
progressively converts into two signals consistent with a A2BX spin
system (X ¼ 31P) agrees with the presence of a thermally activated
exchange process which renders the three hydrides equivalent, at
the NMR time scale, at room temperature. This behaviour was
already observed for other four-legged piano stool iridium trihy-
drides [18]. In Fig. 4 we present the 31P decoupled 1H NMR spectra
of the hydride region of compound 5 at different temperatures. At
298 K, the spectrum shows a singlet that broadens when the
temperature of the sample is lowered. At 238 K, a decoalescence
occurs and, at 218 K, a well resolved A2B spin system is observed.
Line-shape analysis performed using gNMR software, allowed us to
establish that this system is defined by chemical shifts of dA ¼ ꢀ13.6
and dB ¼ ꢀ12.3 ppm and a coupling constant JAB ¼ 173.5 Hz.
When the temperature is further lowered from 218 to 178 K, the
values of the chemical shifts do not change significantly with the
temperature but the value of JAB decreases from 173.5 Hz at 218 K to
81.7 Hz at 178 K. The high value of JAB and its variation with the
temperature indicates that this compound displays quantum
mechanical exchange coupling between HA and HB [4].
iridium atom
h
5-coordinated to a pentamethylcyclopentadienyl
ligand (Cp*), and to three monodentate ligands leading to the
formation of a “three-legged piano stool” structure. These ligands are
a chloride ligand, a carbonyl ligand and a diphenylmethylphosphane
ligand. The geometry of the complex is pseudo octahedral and is
marked by near90ꢁ valuesfortheanglesC(0)eIreP(1), C(0)eIreCl(1)
and P(1)eIreCl(1), less than 1ꢁ far from the regularity.
The centroid of Cp* ligand is situated at 1.8814(4) Å from the
iridium atom, and the average IreC bond distances for the Cp*
ligand is 2.2403(9) Å (Table 2), being both values similar to those
found in the literature [14].
The IreC(0) and IreCl bond lengths [1.89(2) Å and 2.383(3) Å,
respectively] are in good agreement with the scarce values found in
the literature for structures based on the {Cp*Ir(CO)Cl} fragment
[15]. Less data were found containing the {Cp*Ir(PMePh2)} frag-
ment, but the IreP bond length [2.334(2) Å], compares well with
that found in the cation [Cp*Ir(PMe3)(mesityl)(CO)]þ [14b]. The
disposition of the phosphane ligand is in such a way that the methyl
group is situated pseudo-trans to the chlorine ligand, perhaps due
the steric hindrance of the Cp* ligand.
2.3. Protonation studies of compounds 1 and 2
With the aim of obtaining dihydrogen compounds by proton-
ation of the dihydride complexes 1 and 2, we treated a diethyl
ether solution of the dihydrides with slight excess of HBF4$Et2O.
The reaction was carried out at low temperature due to the low
thermal stability of most of the dihydrogen complexes [16].
Reaction of the dihydride 2 yielded a brown solid insoluble in the
common solvents that cannot be identified [17]. In the case of
The T1 values of the hydrogen nuclei of the IrH3 unit of 5 were
determined over the temperature range 298e178 K. T1(min) values
of 137 ms for HA, and 151 ms for HB were obtained at 204 K and
Scheme 2.

116
M. Talavera et al. / Journal of Organometallic Chemistry 715 (2012) 113e118
Table 2
Crystal data and structure refinement for [Cp*IrCl(PPh2Me)(CO)]BPh4 (4).
Empirical formula
Formula weight
Temperature
C48H48BClOPIr
910.29
293(2) K
Wavelength
0.71073 Å
Crystal system
Space group
Monoclinic
P21/n
Unit cell dimensions
a ¼ 15.8833(14) Å
b ¼ 11.0778(10) Å
c ¼ 23.751(2) Å
b
¼ 94.102(2)ꢁ
Volume
4168.4(6) Å [3]
Z
4
Density (calculated)
Absorption coefficient
F(000)
1.451 Mg/m3
3.340 mmꢀ1
1832
Crystal size
Theta range for data collection
Index ranges
Reflections collected
Independent reflections
Reflections observed (>2
Data completeness
0.18 ꢂ 0.11 ꢂ 0.10 mm
1.49e28.01ꢁ
ꢀ20 ꢃ h ꢃ 20; ꢀ14 ꢃ k ꢃ 10; ꢀ25 ꢃ l ꢃ 31
27 125
9959 [R(int) ¼ 0.0971]
s)
4111
0.987
Absorption correction
Max. and min. transmission
Refinement method
Semi-empirical from equivalents
0.7456/0.6484
Full-matrix least-squares on F2
9959/0/481
Data/restraints/parameters
Goodness-of-fit on F2
0.959
Fig. 3. ORTEP view of the cationic complex [Cp*IrCl(PPh2Me)(CO)]þ drawn at 30%
probability level. Hydrogen atoms are omitted for clarity.
Final R indices [I > 2
R indices (all data)
Largest diff. peak and hole
s
(I)]
R1 ¼ 0.0513 wR2 ¼ 0.1058
R1 ¼ 0.1825 wR2 ¼ 0.1572
1.006 and ꢀ1.885 eÅꢀ3
206 K respectively, supporting the classical trihydride character of
5 [19].
temperature at 400 MHz using a standard inversion-recovery
methodology. Coupling constants are given in Hertz. Infrared
spectra were run on a Jasco FT/IR-6100 spectrometer using KBr
pellets. C, H, and N analyses were carried out in Carlo Erba 1108
analyzer. High resolution electrospray mass spectra were acquired
using an Apex-Qe spectrometer.
3. Experimental
3.1. General procedures, methods and materials
All experiments were carried out under an atmosphere of argon
by Schlenk techniques. Solvents were dried by the usual procedures
[20] and distilled under argon prior to use. The starting materials
[Cp*IrCl2(PPh2Me)] [21], [Cp*IrCl2(PTA)] [22] were prepared as
described in the literature. All reagents were obtained from
commercial sources. Unless stated, NMR spectra were recorded at
room temperature on Bruker ARX-400 instrument, with resonating
3.2. X-ray diffraction analysis
Crystallographic data of [Cp*IrCl(PPh2Me)(CO)]BPh4 (4) were
collected on a Bruker Smart 1000 CCD diffractometer at CACTI
(Universidade de Vigo) using graphite monochromated Mo-K
radiation (
a
l
¼ 0.71073 Å), and were corrected for Lorentz and
polarisation effects. The software SMART [24] was used for col-
lecting frames of data, indexing reflections, and the determination
of lattice parameters, SAINT [25] for integration of intensity of
reflections and scaling, and SADABS [26] for empirical absorption
correction.
frequencies of 400 MHz (1H), 161 MHz (31P{1H}), and 100 MHz (13
C
{1H}) using the solvent as the internal lock. 1H and 13C{1H} signals
are referred to internal TMS and those of 31P{1H} to 85% H3PO4;
downfield shifts (expressed in ppm) are considered positive. 1H and
13C{1H} NMR signal assignments were confirmed by 1H-COSY,
HSQC (1He13C), HMBC (1He13C) and DEPT experiments. Low-
temperature measurements were made by cooling the probe with
a stream of N2. NMR spectra were simulated using gNMR 4.1 soft-
ware [23]. T1 relaxation times for the hydridic resonances of
complexes were measured in CD2Cl2 or Toluene-d8 as a function of
The crystallographic treatment of the compound was performed
with the Oscail program [27]. The structure was solved by direct
methods and refined by a full-matrix least-squares based on F2 [28].
All non-hydrogen atoms were refined with anisotropic displace-
ment parameters. Hydrogen atoms were included in idealized
positions and refined with isotropic displacement parameters.
Details of crystal data and structural refinement are given in
Table 2.
Table 1
Selected bond lengths (Å) and angles (ꢁ) for compound 4.
IreC(0)
IreCl(1)
IreC(1)
IreC(3)
1.886(12)
2.383(3)
2.197(8)
2.237(9)
2.268(9)
126.6(3)
121.51(7)
90.1(3)
IreP(1)
IreCT*
IreC(2)
IreC(4)
2.334(2)
1.8814(4)
2.234(9)
2.261(9)
IreC(5)
CT*eIreC(0)
CT*eIreCl(1)
C(0)eIreCl(1)
O(1)eC(0)eIr
CT*eIreP(1)
C(0)eIreP(1)
P(1)eIreCl(1)
127.95(6)
89.2(3)
90.17(9)
175.3(12)
CT* refers to the centroid of Cp* ligand.
Scheme 3.

M. Talavera et al. / Journal of Organometallic Chemistry 715 (2012) 113e118
117
dissolved in hexane/THF (5:1 v/v). This solution was filtered
through a silica column using methanol as eluent. After that, the
solvent was vacuum removed and the light brown solid obtained
was washed with pentane (3 ꢂ 5 mL) and dried in vacuum. Yield:
126.3 mg (49%).
Method (b): [Cp*IrCl2(PTA)] (300 mg, 0.54 mmol) was added to
a vigorously stirred solution of sodium methoxide prepared by
dissolving sodium (150 mg, 12.75 equiv) in 25 mL of methanol. The
solution was allowed to react for 2 h at reflux temperature, and
then, the solvent was vacuum removed. The residue obtained was
dissolved in toluene (20 mL) and filtered through a CeliteÒ column.
The solvent was vacuum removed again and the brown solid
obtained was washed with pentane (3 ꢂ 5 mL) and dried in
vacuum. Yield: 150 mg (57%).
Anal. Calcd for C16H29N3IrP (486.62 g/mol): C 39.49, H 6.01, N
8.64; found: C 39.93, H 6.07, N 8.69. MS (m/z, referred to the most
abundant isotopes): 486 [M]þ. IR (cmꢀ1):
n (IreH) 2095 (s), 1896 (s).
T1(min): 647 ms (209 K). 1H NMR (C6D6):
d
ꢀ17.91 (d, 2H,
4
2JHeP ¼ 32.5 Hz, IreH); 2.11 (d, 15H, JHeP ¼ 0.6 Hz, C5CH3); 3.63
(s, 6H, PCH2N); 3.99e4.34 (AB system, 6H, NCH2N) ppm. 31P{1H}
NMR (C6D6):
d
ꢀ68.29 (s, P-PTA) ppm. 13C{1H} NMR (C6D6):
d 11.9
(s, C5CH3); 59.2 (d, 1JCeP ¼ 25.1 Hz, PCH2N); 73.6 (d, 3JCeP ¼ 7.0 Hz,
NCH2N); 92.3 (s, C5CH3) ppm.
3.3.3. Preparation of [Cp*IrCl(PPh2Me)(CO)]Cl (3)
A
nitrogen-purged orange solution of [Cp*IrCl2(PPh2Me)]
(100 mg, 0.17 mmol) in 15 mL of methanol was placed in a Schlenk
flask equipped with a Teflon stopcock under an atmosphere of CO
(PCO ¼ 1 atm). The Schlenk tube was tightly closed and heated at
75 ꢁC for 90 min. Removal of the solvent under vacuum and
precipitation of the residue with Et2O (3 ꢂ 5 mL) gave a yellow
solid. The solid was finally dried in vacuum. Yield: 80 mg (75%).
Anal. Calcd for C24H28OCl2IrP (626.68 g/mol): C 45.96, H 4.47;
found: C 45.72, H 4.50. IR (cmꢀ1):
n
(CO) 2042 (s). 1H NMR (CD2Cl2):
Fig. 4. NMR 1H{31P} NMR spectra (400 MHz) in CD2Cl2 at various temperatures in the
hydride region of [Cp*IrH3(PPh2Me)]BF4 (5).
4
2
d
1.85 (d, 15H, JHeP ¼ 2.4 Hz, C5CH3); 2.54 (d, 3H, JHeP ¼ 11.2 Hz,
PPh2CH3); 7.50e7.68 (m, 10H, PPh2CH3) ppm. 31P{1H} NMR
(CD2Cl2):
d
ꢀ12.26 (s, PPh2CH3) ppm. 13C{1H} NMR (CD2Cl2):
d 9.4
(s, C5CH3); 15.1 (d, 1JCeP ¼ 42.6 Hz, PPh2CH3); 105.6 (s, C5CH3); 127.6
3.3. Synthesis and characterization of the complexes
1
1
(d, JCeP ¼ 61.8 Hz, Cipso); 129.0 (d, JCeP ¼ 61.7 Hz, Cipso);
129.4e129.8 (C PPh2Me); 132.6e133.3 (C PPh2Me); 166.1
(d, 2JCeP ¼ 14.3 Hz, CO) ppm.
3.3.1. Preparation of [Cp*Ir(H)2(PPh2Me)](1)
An orange solution of [Cp*IrCl2(PPh2Me)] (515 mg, 0.86 mmol)
in 15 mL of toluene was treated with Red-Al (1.5 mL, 6 equiv). The
reaction mixture was stirred for 15 min. After that, the solvent was
vacuum removed and the resulting “gum” was dissolved in hexane/
THF (5:1 v/v). This solution was filtered through a silica column
using hexane/THF (5:1 v/v) as eluent. The solvent was vacuum
removed and the brown solid obtained was washed with pentane
(3 ꢂ 2 mL) and dried in vacuum. Yield: 168.0 mg (37%). Anal. Calcd.
for C23H30IrP (529.68 g/mol): C 52.15, H 5.71; found: C 52.51, H 5.83.
MS (m/z, referred to the most abundant isotopes): 527 [M ꢀ 2H]þ.
3.3.4. Preparation of [Cp*IrCl(PPh2Me)(CO)]BPh4 (4)
A metathesis reaction carried out by treating complex 3 dis-
solved in warm MeOH with an excess of NaBPh4 yielded complex 4.
Yellow crystals of 4 were obtained by slow evaporation of the
solvent. 1H NMR (CD2Cl2):
d
1.66 (d, 15H, JHeP ¼ 2.4 Hz, C5CH3);
4
2
2.32 (d, 3H, JHeP ¼ 11.2 Hz, PPh2CH3); 6.80e6.89 (m, 4H, BPh4);
6.99 (t, 8H, JHeB ¼ 7.4 Hz, BPh4); 7.25e7.34 (m, 8H, BPh4); 7.44e7.71
(m, 10H, PPh2CH3) ppm. 31P{1H} NMR (CD2Cl2):
(s, PPh2CH3) ppm.
d
ꢀ11.93
IR (cmꢀ1):
NMR (CD2Cl2):
n
(IreH) 2109 (m), 1922 (m). T1(min): 459 ms (200 K). 1H
d
ꢀ17.83 (d, 2H, 2JHeP ¼ 31.4 Hz, IreH); 1.91 (d, 15H,
4JHeP ¼ 2.0 Hz, C5CH3); 2.11 (d, 3H, JHeP ¼ 9.6 Hz, PPh2CH3);
2
3.3.5. Preparation of [Cp*IrH3(PPh2Me)]BF4 (5)
A brown solution of [Cp*Ir(H)2(PPh2Me)] (130 mg, 0.25 mmol)
in 4 mL of diethyl ether was cooled in an ice bath and then
7.25e7.38 (m, 6H, PPh2CH3); 7.47e7.55 (m, 4H, PPh2CH3) ppm. 31P
{1H} NMR (CD2Cl2):
d
ꢀ5.57 (s, PPh2CH3) ppm. 13C{1H} NMR
(CD2Cl2):
d
10.9 (s, C5CH3); 24.7 (d, 1JCeP ¼ 41.9 Hz PPh2CH3); 92.3
HBF4$Et2O (35.9 mL, 0.295 mmol) was added. Immediately, a brown
(d, 2JCeP ¼ 3.0 Hz, C5CH3); 127.9 (d, 3JCeP ¼ 9.9 Hz, C PPh2Me); 129.4
(d, 4JCeP ¼ 2.3 Hz, C PPh2Me); 132.6 (d, 2JCeP ¼ 10.9 Hz, C PPh2Me);
139.3 (d, 1JCeP ¼ 51.4 Hz, Cipso) ppm.
solid appeared. This solid was separated by decantation, washed
with diethyl ether (3 ꢂ 2 mL) and dried in vacuum. Yield: 108.9 mg
(70%). Anal. Calcd for C23H31BF4IrP (617.50 g/mol): C 44.74, H 5.06;
found: C 44.55, H 5.13. MS (m/z, referred to the most abundant
isotopes): 531 [MeH3eBF4]þ. IR (cmꢀ1):
n (IreH) 2143 (m), 2101
3.3.2. Preparation of [Cp*Ir(H)2(PTA)] (2)
(w). T1(min): 137 ms and 151 ms. 1H NMR (CD2Cl2):
d
ꢀ13.01 (d, 3H,
Method (a): A yellow solution of [Cp*IrCl2(PTA)] (300 mg,
0.54 mmol) in 15 mL of toluene was treated with Red-Al (2.5 mL, 15
equiv). The reaction mixture was stirred for 2 h at room tempera-
ture. Solvent was vacuum removed and the resulting oil was
2JHeP ¼ 9.2 Hz, IreH); 2.05 (d, 15H, JHeP ¼ 1.7 Hz, C5CH3); 2.35
4
2
(d, 3H, JHeP ¼ 10.9 Hz, PPh2CH3); 7.40e7.50 (m, 4H, PPh2CH3);
7.50e7.57 (m, 6H, PPh2CH3) ppm. 31P{1H} NMR (CD2Cl2):
d
ꢀ8.30

118
M. Talavera et al. / Journal of Organometallic Chemistry 715 (2012) 113e118
(s, PPh2CH3) ppm. 13C{1H} NMR (CD2Cl2):
d 10.1 (s, C5CH3); 22.2
[9] M.A. Salomon, T. Braun, I. Krossing, Dalton Trans. (2008) 5197.
[10] (a) P.J. Desrosiers, L. Cai, Z. Lin, R. Richards, J. Halpern, J. Am. Chem. Soc. 113
(1991) 4173;
(b) C.A. Bayse, R.L. Luck, E.J. Schelter, Inorg. Chem. 40 (2001) 3463.
[11] It is not unusual that methanol (employed here as a solvent) produces
carbonylation of hydride complexes. On the other hand, formation of meth-
oxide species such as [Cp*Ir(OMe)2(PPh2Me]þ or [Cp*Ir(OMe)Cl(PPh2Me]þ,
can be ruled out because there are no signals in the 1H and 13C{1H} NMR
spectra of the mixture compatible with the presence of the OCH3 group.
[12] D. Wang, R.J. Angelici, Inorg. Chem. 35 (1996) 1321.
1
(d, JCeP
¼
46.6 Hz, PPh2CH3); 103.7 (s, C5CH3); 129.5 (d,
2JCeP ¼ 11.6 Hz, C PPh2Me); 131.3 (d, 1JCeP ¼ 65.9 Hz, Cipso); 131.9 (d,
3JCeP ¼ 10.9 Hz, C PPh2Me); 132.6 (d, 4JCeP ¼ 2.8 Hz, C PPh2Me) ppm.
4. Conclusions
The synthesis of half-sandwich dihydride complexes of iri-
dium(III) containing P-donor ligands such as PPh2Me and 1,3,5-
triaza-7-phosphaadamantane (PTA) has been achieved using
[Cp*Ir(Cl)2(PR3)]; (PR3 ¼ PPh2Me, PTA) as a precursor. Proton-
ation of [Cp*Ir(H)2(PPh2Me)] with HBF4$Et2O does not give an
[13] Experimental and spectroscopic details for [Cp*IrH(CO)(PPh2Me)]PF6ꢀ. A
green solution of the mixture in 5 mL of methanol was treated with NaPF6.
The reaction mixture was stirred for 15 min. After that, the solvent was
vacuum removed and the resulting oil was dissolved in CH2Cl2. This solution
was filtered, the solvent was vacuum removed and the red oil obtained
washed with pentane (3 ꢂ 2 mL) and finally dried in vacuum. IR (cmꢀ1):
2-H2 complex but proceeds with the formation of the classical
n
d
(IreH) 2115 (w), 1979 (w); (CO) 2034 (s); (PF6) 840 (s). 1H NMR (CD2Cl2):
h
2
4
ꢀ14.71 (d, 1H, JHeP ¼ 27.4 Hz, IreH); 1.99 (dd, 15H, JHeP ¼ 2.2 Hz,
trihydride [Cp*Ir(H)3(PPh2Me)](BF4) which displays quantum
mechanical exchange coupling between the hydrogen nuclei.
Preliminary results indicate that the new neutral and cationic
hydride complexes display a noticeable chemical inertness.
2
4JHeH ¼ 1.0 Hz, C5CH3); 2.38 (d, 3H, JHeP ¼ 10.8 Hz, PPh2CH3); 7.40e7.64
(m, 10H, PPh2CH3) ppm. 31P{1H} NMR (CD2Cl2):
d
ꢀ144.1 (hept, 1JPeF ¼ 711 Hz,
PF6); ꢀ9.8 (s, PPh2CH3) ppm. 13C{1H} NMR (CD2Cl2):
d 9.8 (s, C5CH3); 20.1
1
2
(d, JCeP
(d, JCeP
(d, JCeP
¼
¼
¼
44.9 Hz, PPh2CH3); 102.7 (d, JCeP
¼
1.5 Hz, C5CH3); 128.2
9.1 Hz, PPh2Me); 129.9
64.0 Hz, Cipso); 132.1
1
3
63.0 Hz, Cipso); 129.8 (d, JCeP
¼
C
3
1
9.0 Hz,
C
PPh2Me); 130.1 (d, JCeP
¼
Acknowledgements
(d, JCeP ¼ 3.0 Hz, C PPh2Me); 132.2 (d, JCeP ¼ 3.0 Hz, C PPh2Me); 132.8
(d, JCeP ¼ 3.0 Hz, C PPh2Me); 133.0 (d, JCeP ¼ 3.0 Hz, C PPh2Me; 166.5
2
(d, JCeP ¼ 10.0 Hz, CO) ppm.
We thank the University of Vigo CACTI services for collecting
X-ray data and recording NMR spectra. M.T. acknowledges the
University of Vigo for a Master grant.
[14] (a) D. Monti, G. Frachey, M. Bassetti, A. Haynes, G.J. Sunley, P.M. Maitlis,
A. Cantoni, G. Bocelli, Inorg. Chim. Acta 240 (1995) 485;
(b) P.J. Alaimo, B.A. Arndtsen, R.G. Bergman, Organometallics 19 (2000) 2130;
(c) P. Kumar, M. Yadav, A.K. Singh, D.S. Pandey, Eur. J. Inorg. Chem (2010) 704.
[15] C. Hammons, X. Wang, V. Nesterov, M.G. Richmond, J. Chem. Cryst. 40 (2010)
453.
Appendix A. Supplementary material
[16] X.R.L. Fontaine, E.H. Fowles, B.L. Shaw, J. Chem. Soc. Chem. Commun. (1998) 482.
[17] Although the first equivalent of acid to a complex bearing PTA ligands,
usually goes to one of the PTA nitrogen atoms (this fact is easily confirmed by
the 1H NMR spectrum because it is reflected in a more complicated pattern of
the signals corresponding to the PTA methylene protons), in our case the
addition of two equivalents of acid to complex 2 also gave a solid residue. The
31P{1H} NMR spectrum of the soluble fraction of the solid residue showed
a mixture of several unidentified compounds.
CCDC 865154 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
References
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with 1,1-diphenyl-2-propyn-1-ol gave a mixture of unidentified products.
With the aim to obtain a dihydrogen complex, we have also treated complex 5
with HBF4, but there is no reaction either.
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