Preparation and reactivity of iridium(III) hydride complexes with pyrazole and imidazole ligands

Article abstract of DOI:10.1016/j.jorganchem.2005.11.004

Pyrazole IrHCl₂(HRpz)P₂ [P = PPh₃, P ⁱPr₃; R = H, 3-Me], bis(pyrazole) [IrHCl(HRpz) ₂(PPh₃)₂]BPh₄ and imidazole IrHCl₂(HIm)(PPh₃)₂ derivatives were prepared by allowing the IrHCl₂(PPh₃)₃ complex to react with the appropriate azole in refluxing 1,2-dichloroethane. Nitrile IrHCl ₂(CH₃CN)(PPh₃)₂ and 2,2′-bipyridine (bpy) [IrHCl(bpy)(PPh₃)₂]BPh ₄ derivatives were also prepared using IrHCl₂(PPh ₃)₃ as a precursor. The complexes were characterised spectroscopically (IR and NMR) and a geometry in solution was also established. Protonation with Br?nsted acid of pyrazole IrHCl₂(Hpz) (PPh₃)₂ and imidazole IrHCl₂(HIm)(PPh ₃)₂ complexes proceeded with the loss of the azole ligands and the formation of the unstable IrHCl₂(PPh₃) ₂ derivative. Vinyl IrCl₂{CHC(H)R1}(HRpz)P₂ and IrCl₂{CHC(H)R1}(HIm)P₂ (R1 = Ph, p-tolyl, COOCH ₃; P = PPh₃, PⁱPr₃) complexes were prepared by allowing hydride-pyrazole IrHCl₂(HRpz)P₂ and hydride-imidazole IrHCl₂(HIm)P₂ to react with an excess of terminal alkyne in 1,2-dichloroethane. The complexes were characterised spectroscopically and by the X-ray crystal structure determination of the IrCl₂{CHC(H)Ph}(Hpz)(PPh₃)₂ derivative.

Full text of DOI:10.1016/j.jorganchem.2005.11.004

Journal of Organometallic Chemistry 691 (2006) 1012–1024
www.elsevier.com/locate/jorganchem
Preparation and reactivity of iridium(III) hydride complexes
with pyrazole and imidazole ligands
a,
a
b
b
*
´
´
Gabriele Albertin , Stefano Antoniutti , Jesus Castro , Soledad Garcia-Fontan ,
a
Enerida Gurabardhi
a
`
Dipartimento di Chimica, Universita Caꢀ Foscari di Venezia, Dorsoduro 2137, 30123 Venice, Italy
Departamento de Quı´mica Inorga´nica, Universidade de Vigo, Facultade de Quı´mica, Edificio de Ciencias Experimentais, 36310 Vigo (Galicia), Spain
b
Received 3 October 2005; received in revised form 25 October 2005; accepted 7 November 2005
Available online 19 December 2005
Abstract
Pyrazole IrHCl2(HRpz)P2 [P = PPh3, PiPr3; R = H, 3-Me], bis(pyrazole) [IrHCl(HRpz)2(PPh3)2]BPh4 and imidazole IrHCl2-
(HIm)(PPh3)2 derivatives were prepared by allowing the IrHCl2(PPh3)3 complex to react with the appropriate azole in refluxing 1,2-
dichloroethane. Nitrile IrHCl2(CH3CN)(PPh3)2 and 2,20-bipyridine (bpy) [IrHCl(bpy)(PPh3)2]BPh4 derivatives were also prepared using
IrHCl2(PPh3)3 as a precursor. The complexes were characterised spectroscopically (IR and NMR) and a geometry in solution was also
established. Protonation with Brønsted acid of pyrazole IrHCl2(Hpz)(PPh3)2 and imidazole IrHCl2(HIm)(PPh3)2 complexes proceeded
with the loss of the azole ligands and the formation of the unstable IrHCl2(PPh3)2 derivative. Vinyl IrCl2{CH@C(H)R1}(HRpz)P2 and
IrCl2{CH@C(H)R1}(HIm)P2 (R1 = Ph, p-tolyl, COOCH3; P = PPh3, PiPr3) complexes were prepared by allowing hydride-pyrazole
IrHCl2(HRpz)P2 and hydride-imidazole IrHCl2(HIm)P2 to react with an excess of terminal alkyne in 1,2-dichloroethane. The complexes
were characterised spectroscopically and by the X-ray crystal structure determination of the IrCl2{CH@C(H)Ph}(Hpz)(PPh3)2
derivative.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Hydride; Pyrazole and imidazole ligands; P ligands; Iridium; Vinyl
1. Introduction
carried out to understand and rationalise the influence of
the ancillary ligands on the reactivity of the M–H bond
of transition metal polyhydrides and in this context the
important role of the N-donor ligands is emerging [1,3–7].
We have interest in the chemistry of classical and non-
classical transition metal hydrides and have previously
reported the synthesis and the reactivity of several mono
and dihydrides of the manganese(I), iron(II) and cobalt(III)
triads stabilised by monodentate phosphite ligands [8].
Recently we have also extended these studies with the
aim of introducing nitrogen-donor ligands in hydride
chemistry and have reported the synthesis and reactivity
of mixed-ligand [MH(N-N)P3]+ (M = Fe, Ru, Os) hydride
complexes with phosphite and polypyridyls [9]. The further
extension of these studies to the isoelectronic d6 irid-
ium(III) has been suggested [10] by the properties of the
IrHCl2(PPh3)3 complex, in which one triphenylphosphine
Transition metals hydrides are an important class of
compounds which continue to be studied, not only for their
chemical and spectroscopic properties, but also because
they are involved in many catalytic processes [1,2]. Among
the ligands used to stabilise the hydride complexes, p-
acceptors such as carbonyl, mono and polydentate phos-
phine and cyclopentadienyls play a prominent role [1]. Less
attention has been devoted to the use of N-donor molecules
such as imidazole, pyrazole [3–5] or polypyridyls [6],
although the introduction of one or more of these groups
in the coordination sphere of the metal may greatly change
the properties of the M–H bond. Several studies have been
*
Corresponding author. Fax: +39 041 234 8917.
E-mail address: albertin@unive.it (G. Albertin).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.11.004

G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
1013
ligand is rather labile and can be easily substituted by sev-
eral ligands. The IrHCl2(PPh3)3 species can therefore be
used as a precursor to introduce N-donor molecules into
hydride complexes of Ir(III). The results of our studies,
which allowed the synthesis and some reactivity of irid-
ium(III) hydrides containing pyrazole, imidazole and 2,20-
bipyridine, are reported here.
An excess of NaBPh4 (0.96 mmol, 0.33 g) in 2 mL of
ethanol was added to the mother liquor of the reaction
and the solution stirred until a yellow solid separated
out, which was filtered and crystallised from CH2Cl2 and
ethanol. The solid is the bis(pyrazole) complex 2 [191 mg,
33% (2a), 202 mg, 34% (2b)]. Found: C, 54.88; H, 4.21;
Cl, 8.06; N, 3.15. C39H35Cl2IrN2P2 (1a) requires C, 54.67;
H, 4.12; Cl, 8.28; N, 3.27%. Found: C, 55.02; H, 4.36; Cl,
8.31; N, 3.33. C40H37Cl2IrN2P2 (1b) requires C, 55.17; H,
4.28; Cl, 8.14; N, 3.22%. Found: C, 65.34; H, 5.01; Cl,
2.78; N, 4.69. C66H59BClIrN4P2 (2a) requires C, 65.59;
H, 4.92; Cl, 2.93; N, 4.64%. KM = 56.6 Xꢀ1 molꢀ1 cm2.
Found: C, 65.89; H, 5.10; Cl, 2.66; N, 4.43. C68H63-
BClIrN4P2 (2b) requires C, 66.04; H, 5.13; Cl, 2.87; N,
4.53%. KM = 58.2 Xꢀ1 molꢀ1 cm2.
2. Experimental
2.1. General comments
All synthetic work was carried out in an appropriate
atmosphere (Ar, N2) using standard Schlenk techniques or
a vacuum atmosphere dry-box. Once isolated, the com-
plexes were found to be relatively stable in air, but were
stored in an inert atmosphere at ꢀ25 ꢁC. All solvents were
dried over appropriate drying agents, degassed on a vacuum
line, and distilled into vacuum-tight storage flasks. IrCl3 was
a Pressure Chemical Co. (USA) product, used as received.
Pyrazole (Hpz), 3-methylpyrazole (H-3-Mepz), imidaz-
ole (HIm), 2,20-bipyridine (bpy) and alkynes RC„CH
(R = Ph, p-tolyl, tBu, COOMe) were Aldrich products used
without further purification. Other reagents were pur-
chased from commercial sources (Aldrich, Fluka) in the
highest available purity and used as received. Infrared spec-
tra were recorded on Nicolet Magna 750 FT-IR or Perkin–
Elmer Spectrum One spectrophotometers. NMR spectra
(1H, 31P, 13C) were obtained on AC200 or AVANCE 300
Bruker spectrometers at temperatures between ꢀ90 and
2.2.2. [IrHCl(HRpz)2(PPh3)2]BPh4 (2) [R = H (a),
3-Me (b)]
Method 2. An equimolar amount of CF3SO3H (26.5 lL,
0.30 mmol) was added to a solution of IrH2Cl(PPh3)3
(0.30 g, 0.30 mmol) in CH2Cl2 (10 mL) cooled to
ꢀ196 ꢁC. The reaction mixture was brought to room tem-
perature, stirred for 1 h and then an excess of pyrazole
(1.0 mmol, 68 mg) was added. The solution was stirred
for 5 h and then the solvent removed under reduced pres-
sure to give a yellow solid which was treated with ethanol
(5 mL) containing an excess of NaBPh4 (0.6 mmol,
0.21 g). A yellow solid slowly separated out from the
resulting solution, which was filtered and crystallised from
CH2Cl2 and ethanol [207 mg, 57% (2a), 200 mg, 54% (2b)].
1
+30 ꢁC, unless otherwise noted. H and 13C spectra are
referred to internal tetramethylsilane; 31P{1H} chemical
shifts are reported with respect to 85% H3PO4 with down-
field shifts considered positive. The COSY, HMQC and
HMBC NMR experiments were performed using their
standard programs. The SwaN-MR software package [11]
was used to treat NMR data. The conductivity of
10ꢀ3 mol dmꢀ3 solutions of the complexes in CH3NO2 at
25 ꢁC were measured with a Radiometer CDM 83.
2.2.3. IrHCl2(Hpz)(PiPr3)2 (3)
An excess of pyrazole (68 mg, 1 mmol) was added to a
solution of IrHCl2(PiPr3)2 (0.200 g, 0.34 mmol) in 10 mL
of ClCH2CH2Cl and the reaction mixture was refluxed for
2 h. The solvent was removed under reduced pressure to
give an oil which was triturated with ethanol (2 mL). A yel-
low solid slowly separated out which was filtered and crys-
tallised from CH2Cl2 and ethanol (180 mg, 81%). Found: C,
38.81; H, 7.36; Cl, 10.62; N, 4.35. C21H47Cl2IrN2P2 requires
C, 38.64; H, 7.26; Cl, 10.86; N, 4.29%.
2.2. Synthesis of complexes
The mer- and fac-IrHCl2(PPh3)3, IrH2Cl(PPh3)3 and
IrHCl2(PiPr3)2 hydrides were prepared following the
reported methods [12,13].
2.2.4. IrHCl2(HIm)(PPh3)2 (4)
An excess of imidazole (2 mmol, 136 mg) was added to a
solution of IrHCl2(PPh3)3 (0.50 g, 0.48 mmol) in 15 mL of
1,2-dichloroethane and the reaction mixture refluxed for
4 h. The solvent was removed under reduced pressure to
give an oil which was triturated with ethanol (3 mL). A yel-
low solid slowly separated out which was filtered and crys-
tallised from CH2Cl2 and ethanol (238 mg, 58%). Found:
C, 54.90; H, 4.22; Cl, 8.15; N, 3.25. C39H35Cl2IrN2P2
requires C, 54.67; H, 4.12; Cl, 8.28; N, 3.27%.
2.2.1. IrHCl2(HRpz)(PPh3)2 (1) and [IrHCl(HRpz)2-
(PPh3)2]BPh4 (2) [R = H (a), 3-Me (b)]
Method 1. An excess of the appropriate pyrazole
(1.44 mmol) was added to a solution of mer-IrHCl2(PPh3)3
(0.50 g, 0.48 mmol) in 50 mL of 1,2-dichloroethane and the
reaction mixture refluxed for 3 h. The solvent was removed
under reduced pressure leaving an oil which was treated
with ethanol (2 mL). A yellow solid slowly separated out
from the resulting solution, which was filtered and crystal-
lised from CH2Cl2 and ethanol. The solid is the monopy-
razole complex 1 [181 mg, 44% (1a), 188 mg, 45% (1b)].
2.2.5. IrHCl2(CH3CN)(PPh3)2 (5)
An excess of CH3CN (3 mmol, 0.16 mL) was added to a
solution of IrHCl2(PPh3)3 (0.50 g, 0.48 mmol) in 15 mL of
1,2-dichloroethane and the reaction mixture refluxed for

1014
G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
4 h. The solvent was removed under reduced pressure to
give an oil which was triturated with ethanol (3 mL). A yel-
low solid slowly separated out which was filtered and crys-
tallised from CH2Cl2 and ethanol (299 mg, 75%). Found:
C, 55.18; H, 4.23; Cl, 8.70; N, 1.72. C38H34Cl2IrNP2
requires C, 55.01; H, 4.13; Cl, 8.55; N, 1.69%.
(0.17 g, 0.2 mmol) as a precursor [134 mg, 70% (10a),
132 mg, 68% (10b)]. Found: C, 58.99; H, 4.48; Cl, 7.18;
N, 2.90. C47H41Cl2IrN2P2 (10a) requires C, 58.87; H,
4.31; Cl, 7.39; N, 2.92%. Found: C, 59.49; H, 4.50; Cl,
7.38; N, 2.82. C48H43Cl2IrN2P2 (10b) requires C, 59.26;
H, 4.45; Cl, 7.29; N, 2.88%.
2.2.6. [IrHCl(bpy)(PPh3)2]BPh4 (6) (bpy = 2,20-
bipyridine)
2.2.11. IrCl2{g1-C(O)CH2C(CH3)3}(PPh3)2 (11)
An equimolar amount of CF3SO3H (10.6 lL,
In a 50-mL three-necked round-bottomed flask were
placed 0.50 g (0.48 mmol) of IrHCl2(PPh3)3, 0.22 g (excess,
1.41 mmol) of 2,20-bipyridine and 15 mL of 1,2-dichloro-
ethane. The resulting solution was refluxed for 3 h and then
the solvent was removed under reduced pressure. The
brown oil obtained was treated with ethanol (4 mL) con-
taining an excess of NaBPh4 (0.328 g, 0.96 mmol). A yel-
low-orange solid slowly separated out which was filtered
and crystallised from CH2Cl2 and ethanol (372 mg, 63%).
Found: C, 68.25; H, 4.68; Cl, 2.64; N, 2.25. C70H59-
BClIrN2P2 requires C, 68.43; H, 4.84; Cl, 2.89; N, 2.28%.
0.12 mmol) was added to
a
solution of IrHCl2-
(HIm)(PPh3)2 (0.200 g, 0.23 mmol) in 8 mL of CH2Cl2
cooled to ꢀ196 ꢁC and the reaction mixture, brought to
room temperature, stirred for 1 h. An excess of
(CH3)3CC„CH (0.46 mmol, 58 lL) was added and the
solution stirred at room temperature for 24 h. The solvent
was removed under reduced pressure to give an oil which
was triturated with ethanol (2 mL). A yellow solid slowly
separated out which was filtered and crystallised from
CH2Cl2 and ethanol (78 mg, 38%). Found: C, 57.02; H,
4.78; Cl, 8.12. C42H41Cl2IrOP2 requires C, 56.88; H, 4.66;
Cl, 8.00%.
K
M = 60.4 Xꢀ1 molꢀ1 cm2.
2.2.7. IrCl2{CH@C(H)R1}(Hpz)(PPh3)2 (7) [R1 = Ph
(a), p-tolyl (b), COOCH3 (c)]
2.2.12. Protonation reactions
The protonation of IrH2Cl(PPh3)3, IrHCl2(Hpz)(PPh3)2
and IrHCl2(HIm)(PPh3)2 complexes was studied in a NMR
tube by 1H and 31P spectra collected between +20 and
ꢀ80 ꢁC. A typical experiment involved the addition of a
CD2Cl2 solution (0.5 mL) of the appropriate hydride com-
pound (0.03–0.04 mmol) in a screw-cap 5-mm NMR tube
placed in a vacuum-atmosphere dry-box. The tube was
sealed, cooled to ꢀ80 ꢁC, and then increasing amounts of
CF3SO3H or HBF4Et2O (from 0.5 to 3 equiv.) were added
by a microsyringe. The tube was transferred into the instru-
mentꢀs probe pre-cooled to ꢀ80 ꢁC and the spectra
collected.
An excess of the appropriate alkyne R1C„CH
(1.2 mmol) was added to a solution of the pyrazole
IrHCl2(Hpz)(PPh3)2 complex (0.2 mmol) in 25 mL of 1,2-
dichloroethane and the reaction mixture was refluxed for
3 h. The solvent was removed under reduced pressure to
give an oil which was triturated with ethanol (2 mL). A
red-orange solid separated out which was filtered and crys-
tallised from CH2Cl2 and ethanol [144 mg, 75% (7a),
132 mg, 68% (7b), 135 mg, 72% (7c)]. Found: C, 59.03;
H, 4.44; Cl, 7.61; N, 2.80. C47H41Cl2IrN2P2 (7a) requires
C, 58.87; H, 4.31; Cl, 7.39; N, 2.92%. Found: C, 59.34;
H, 4.55; Cl, 7.12; N, 2.75. C48H43Cl2IrN2P2 (7b) requires
C, 59.26; H, 4.45; Cl, 7.29; N, 2.88%. Found: C, 54.65;
H, 4.26; Cl, 7.41; N, 3.07. C43H39Cl2IrN2O2P2 (7c) requires
C, 54.89; H, 4.18; Cl, 7.54; N, 2.98%.
2.2.13. X-ray crystal structure determination of IrCl2-
{CH@(CH)Ph}(Hpz)(PPh3)2 (7a)
The data collection was taken on a SIEMENS Smart
CCD area-detector diffractometer with graphite-mono-
chromated Mo Ka radiation. Absorption correction were
carried out using SADABS [14]. The structure was solved by
Patterson methods and refined by a full-matrix least-
squares based on F2 [15]. Non-hydrogen atoms were
refined with anisotropic displacement parameters. Hydro-
gen atoms were included in idealised positions and refined
with isotropic displacement parameters except those
bound to the nitrogen atoms of the vinyl ligand, which
were located on Fourier maps and refined isotropically.
Atomic scattering factors and anomalous dispersion cor-
rections for all atoms were taken from International
Tables for X-ray Crystallography [16]. Details of crystal
data and structural refinement are given in Table 1. Crys-
tallographic data in CIF format has been deposited at the
Cambridge Crystallographic Data Centre, CCDC No.
285382.
2.2.8. IrCl2{CH@C(H)Ph}(H-3-Mepz)(PPh3)2 (8a)
This complex was prepared exactly like the related com-
plexes 7 [134 mg, 69%]. Found: C, 59.05; H, 4.53; Cl, 7.14;
N, 2.75. C48H43Cl2IrN2P2 requires C, 59.26; H, 4.45; Cl,
7.29; N, 2.88%.
2.2.9. IrCl2{CH@C(H)Ph}(Hpz)(Pi Pr3)2 (9a)
This complex was prepared exactly like the related tri-
phenylphosphine derivative 7, 8 using IrHCl2(Hpz)(PiPr3)2
(0.12 g, 0.2 mmol) as a precursor (113 mg, 75%). Found: C,
46.35; H, 7.18; Cl, 9.21; N, 3.60. C29H53Cl2IrN2P2 requires
C, 46.15; H, 7.08; Cl, 9.39; N, 3.71%.
2.2.10. IrCl2{CH@C(H)R1}(HIm)(PPh3)2 (10)
[R1 = Ph (a), p-tolyl (b)]
These complexes were prepared exactly like the related
pyrazole complexes 7,
8 using IrHCl2(HIm)(PPh3)2

G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
1015
Table 1
compounds in valuable yield. In every case, mixtures of
the two pyrazole derivatives 1 and 2 were always obtained
and were easily separated as pure microcrystalline solids
and characterised.
Crystal data and structure refinement for trans-E-[IrCl2{CH@C(H)Ph}-
(Hpz)(PPh3)2] (7a)
Identification code
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
[IrCl2(pzH)(HC@CH–Ph)(PPh3)2]
C47H41Cl2IrN2P2
958.86
293(2)
0.71073
Triclinic
The bis(pyrazole) [IrHCl(HRpz)2(PPh3)2]+ (2) derivative
can also be prepared by a different route involving the reac-
tion of the dihydride IrH2Cl(PPh3)3 first with triflic acid
and then with an excess of pyrazole, as shown in Scheme 2.
Protonation with triflic acid of IrH2Cl(PPh3)3 probably
gives the dihydrogen [IrHCl(g2-H2)(PPh3)3]+ complex
which loses the labile g2-H2 ligand (1H NMR) [17] yielding
either the triflate IrHCl(j1-OSO2CF3)(PPh3)3 or the penta-
coordinate [IrHCl(PPh3)3]+ cation. Reactions of these
intermediates with an excess of pyrazole give the bis(pyra-
zole) [IrHCl(HRpz)2(PPh3)2]+ (2) derivatives as the only
product formed in high yield. The coordination of one pyr-
azole to give the [IrHCl(HRpz)(PPh3)3]+ intermediate is
followed by the substitution of a PPh3 ligand yielding the
final bis(pyrazole) complex 2.
˚
ꢀ
P1
Unit cell dimensions
˚
a (A)
10.3653(9)
14.0417(12)
15.8703(13)
81.178(2)
72.506(2)
70.040(2)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Density (calculated) (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
2067.4(3)
2
1.540
3.471
)
956
Hydride-pyrazole complexes can also be prepared with
triisopropylphosphine using the IrHCl2(PiPr3)2 species as
a precursor. Reaction of this pentacoordinate iridium com-
plex with an excess of pyrazole proceeds to exclusively give
the neutral IrHCl2(Hpz)(PiPr3)2 (3) complex, which was
isolated in good yield and characterised (Scheme 3).
In contrast with the results obtained with the triphenyl-
phosphine IrHCl2(PPh3)3 complex, the related triisopropyl-
phosphine derivative does not give the formation of any
bis(pyrazole) complex like 2. The use of a long reaction
time produces only some decomposition, decreasing the
yield of 3.
Imidazole also reacts with the IrHCl2(PPh3)3 precursor
in refluxing 1,2-dichloroethane to give the hydride-imidaz-
ole IrHCl2(HIm)(PPh3)2 (4) derivative (Scheme 4).
The reaction was extensively studied under different con-
ditions and shows that only one PPh3 ligand can be easily
Crystal size (mm)
H range for data collection (ꢁ)
Index ranges
0.35 · 0.18 · 0.14
1.55–28.00
ꢀ13 6 h 6 13;
ꢀ18 6 k 6 17;
ꢀ17 6 l 6 20
Reflections collected
13060
Independent reflections
Reflections observed (>2r)
Data completeness
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
9088 [R(int) = 0.0280]
7332
0.910
Semi-empirical from equivalents
1.000000 and 0.806364
Full-matrix least-squares on F2
9088/0/495
0.899
R1 = 0.0363 wR2 = 0.0626
R1 = 0.0503 wR2 = 0.0655
1.225 and ꢀ0.720
ꢀ3
˚
Largest diff. peak and hole (e A
)
3. Results and discussion
3.1. Preparation of the complexes
Both mer- and fac-iridium(III) IrHCl2(PPh3)3 complexes
react with both pyrazole and 3-methylpyrazole (HRpz) to
give first the IrHCl2(HRpz)(PPh3)2 (1) complex, which fur-
ther reacts with pyrazole to yield the final [IrHCl(HRpz)2-
(PPh3)2]+ (2) derivative, as shown in Scheme 1.
The reaction proceeds with the substitution of only one
triphenylphosphine in the IrHCl2(PPh3)3 precursor to give
1, which can undergo substitution of the chlorine ligand by
the HRpz group to yield the final cationic bis(pyrazole)
derivative 2. Both reactions are very slow at room temper-
ature and need reflux conditions to afford the pyrazole
IrH2Cl(PPh3)3 + CF3SO3H
[IrHCl(PPh3)3]+
– H2
or
IrHCl(κ1-OSO2CF3)(PPh3)3
exc. HRpz
– PPh3
[IrHCl(HRpz)2(PPh3)2]+
2
Scheme 2. R = H, a, 3-Me, b.
HRpz,∆
-PPh3
HRpz,∆
IrHCl2(PPh3)3
IrHCl2(HRpz)(PPh3)2
-Cl-
1
exc. Hpz
IrHCl2(PiPr3)2
IrHCl2(Hpz)(PiPr3)2
[IrHCl(HRpz)2(PPh3)2]+
∆
3
2
Scheme 3.
Scheme 1. R = H, a, 3-Me, b.

1016
G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
exc. HIm
-PPh3
sharp triplet between ꢀ19.70 and ꢀ23.50 ppm of the
IrHCl2(PPh3)3
IrHCl2(HIm)(PPh3)2
hydride ligand. In the spectra the signals of the CH protons
of the pyrazole are also present and their attribution (Table
2) is supported by the multiplicity of the signals, by COSY
experiments and by a comparison with literature data
[5,6,20–22]. The 13C spectra of both the mono- (1, 3) and
bis(pyrazole) (2) complexes (Table 3) confirm the presence
of the HRpz ligand and allow us, through HMQC and
HMBC experiments, to assign all the carbon atoms of
the pyrazole.
4
Scheme 4.
substituted yielding the monoimidazole derivative 4 as the
only obtained product.
Mononuclear iridium(III) complexes with pyrazole are
known [7,18] and were obtained either by oxidative addi-
tion of dihydrogen to the iridium(I) Ir(CO)(HRpz)(PPh3)2
to give IrH2(CO)(HRpz)(PPh3)2 derivatives [18], or by
replacing acetone with pyrazole in the [IrH2{(CH3)2-
CO}2(PPh3)2]BF4 precursor giving the [IrH2(Hpz){(CH3)2-
CO}(PPh3)2]+ and [IrH2(Hpz)2(PPh3)2]+ cations [7a,7b].
More rare are the imidazole complexes [19] which involve
the pentakis(amino) [Ir(NH3)5(HIm)]3+ cation and the tet-
rachloroiridate [H2Im][IrCl4(HIm)2] derivatives. The use of
IrHCl2(PPh3)3 and IrHCl2(PiPr3)2 as precursors allows a
new series of both pyrazole and imidazole complexes of
iridium(III) to be easily prepared.
The facile substitution of the triphenylphosphine in the
IrHCl2(PPh3)3 complex prompted us to study the reaction
with other N-donor molecules such as CH3CN and 2,20-
bipyridine (bpy). The results show that IrHCl2(PPh3)3
reacts with either CH3CN or bpy to give the new mixed-
ligand IrHCl2(CH3CN)(PPh3)2 (5) and [IrHCl(bpy)-
(PPh3)2]+ (6) complexes, which were isolated in good yields
and characterised (Scheme 5).
In the temperature range between +20 and ꢀ80 ꢁC the
31P{1H} NMR spectra of the monopyrazole IrHCl2(HRpz)-
(PPh3)2 (1) complex appear as a sharp singlet suggesting
the magnetic equivalence of the two phosphine ligands.
Furthermore, the far-IR spectra of complex 1 show only
one medium-intensity band at 316 (1a) and at 322 (3)
cmꢀ1, attributable to mIrCl of the two chloride ligands in a
mutually trans arrangement. On the basis of these data, a
geometry of type I (Chart 1) can reasonably be proposed
for the mono-pyrazole IrHCl2(HRpz)(PPh3)2 (1)
derivatives.
Instead, the NMR data do not allow us to unambigu-
ously assign a geometry to the cationic bis(pyrazole)
1
[IrHCl(HRpz)2P2]+ (2) derivatives. The H NMR spectra
show only one NH signal and only one set of pyrazole
CH resonances, in agreement with the magnetic equiva-
lence of the two HRpz ligands. The 13C NMR spectra con-
firm this equivalence showing only one set of signals for the
pyrazole carbon atom. In the temperature range between
+20 and ꢀ80 ꢁC the 31P{1H} NMR spectra appear as a
sharp singlet suggesting the magnetic equivalence of the
two PPh3 ligands. On the basis of these data, however,
we cannot decide between geometries II and III for the
bis(pyrazole) [IrHCl(HRpz)2P2]+ (2) derivatives.
The IR spectra of the imidazole IrHCl2(HIm)(PPh3)2 (4)
complex show the mNH at 3424 cmꢀ1 and the mIrH at
2168 cmꢀ1. The 1H NMR spectrum (Table 2) confirms
the presence of both the HIm and hydride ligands, showing
the characteristic NH proton signal of HIm at 8.87 ppm,
while a triplet at ꢀ20.68 ppm is attributed to the hydride
ligand.
Acetonitrile replaces a PPh3 in IrHCl2(PPh3)3 to give the
mono-substituted complex 5, while bpy replaces both the
PPh3 and the Clꢀ ligands yielding the cationic bipyridine
complex 6.
The new mixed-ligand hydride 1–6 complexes with N-
donor molecules and phosphine were separated as a yellow
or orange solid stable in air and in the solution of the most
common organic solvents where they behave either as non-
electrolyte (1, 3, 4, 5) or as 1:1 electrolyte (2, 6) compounds.
Analytical and spectroscopic data (IR and NMR, Tables 2
and 3) support the proposed formulations. The infrared
spectra of the pyrazole complexes 1–3 show a medium-
intensity band at 3322–3282 cmꢀ1 attributed to the mNH
of the pyrazole ligand. A medium-intensity band is also
present at 2266–2144 cmꢀ1 for 1 and 3 and is attributed
to the mIrH of the hydride ligand. Strong support for the
presence of these ligands, however, comes from the proton
NMR spectra, which show a slightly broad signal at 12.45–
10.27 ppm of the NH proton of the HRpz group and a
In the temperature range between +20 and ꢀ80 ꢁC the
31P{1H} NMR spectra of complex 3 appear as a sharp sin-
glet, in agreement with the presence of two magnetically
equivalent phosphine ligands. Taking into account that
the far-IR spectra show only one mIrCl band at 318 cmꢀ1
,
a structure of type-IV (Chart 2) can reasonably be pro-
posed for the imidazole 4 complex.
A related structure (V) with both the phosphine and the
chloride ligands each in a mutually trans position can also
be proposed for the acetonitrile IrHCl2(CH3CN)(PPh3)2
(5) complex. The far-IR shows, in fact, only one mIrCl
absorption at 323 cmꢀ1 indicating the mutually trans posi-
tion of the two chloride ligands, while only one singlet at
ꢀ0.43 ppm is observed in the 31P{1H} spectra, in agree-
ment with the magnetic equivalence of the two phosphorus
nuclei. The IR spectra show a medium-intensity band at
CH3CN
-PPh3
IrHCl2(CH3CN)(PPh3)2
5
IrHCl2(PPh3)3
bpy
[IrHCl(bpy)(PPh3)2]+
6
Scheme 5. bpy = 2,20-bipyridine.

G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
1017
Table 2
Selected IR and NMR spectroscopic data for iridium complexes
Compound
IRa m (cmꢀ1
)
Assgnt
1H NMRb d (J, Hz)
Assgnt
Spin system
A2
31P{1H}NMRb,c
d (J, Hz)
1a
IrHCl2(Hpz)(PPh3)2
3309 m
2203 m
316 m
mNH
mIrH
mIrCl
10.86 s, br
6.89 d
5.80 d
NH
10.19 s
H5 pz
H3 pz
H4 pz
IrH
5.32 t
ꢀ20.94 t
JPH = 14
1b
IrHCl2(H-3-Mepz)(PPh3)2
3322 m
2144 m
mNH
mIrH
10.27 s, br
7.07 s, br
5.52 s, br
1.81 s
NH
A2
7.84 s
H5 pz
H4 pz
CH3
IrH
ꢀ20.85 t
JPH = 14
2a
2b
3
[IrHCl(Hpz)2(PPh3) 2]BPh4
[IrHCl(H-3-Mepz)2(PPh3)2]BPh4
IrHCl2(Hpz)(PiPr3)2
3322 w
334 m
mNH
mIrCl
11.70 s, br
7.27 s, br
7.01 d
NH
A2
A2
A2
ꢀ7.75 s
ꢀ8.59 s
2.90 s
H5 pz
H3 pz
H4 pz
IrH
5.85 t
ꢀ19.70 t
JPH = 18
3282 m
mNH
11.11 s, br
6.07 s, br
5.63 s, br
1.93 s
NH
H5 pz
H4 pz
CH3
IrH
ꢀ19.73 t
JPH = 18
3285 s
2266 s
322 m
mNH
mIrH
mIrCl
12.45 s, br
8.36 s, br
7.68 s, br
6.48 t
2.77 m
1.11 m
NH
H5 pz
H3 pz
H4 pz
CH phos
CH3
ꢀ23.50 t
IrH
JPH = 14
4
IrHCl2(HIm)(PPh3)2
3424 m
2168 m
318 m
mNH
mIrH
mIrCl
8.87 s, br
7.19 s
6.93 d
NH
A2
10.10 s
H2 Im
H4 Im
H5 Im
IrH
6.37 d
ꢀ20.68 t
JPH = 14
5
6
IrHCl2(CH3CN) (PPh3)2
[IrHCl(bpy)(PPh3)2]BPh4
2203 m
323 m
mCN
mIrCl
1.24 s
CH3
IrH
A2
ꢀ0.43 s
ꢀ21.23 t
JPH = 14
2235 w
mIrH
ABX spin syst
dX ꢀ19.15
IrH
AB
dA 2.0
dB ꢀ6.40
JAX = JBX =18
JAB = 16
7a
IrCl2{CH@C(H)Ph}(Hpz)(PPh3)2
3314 m
324 m
mNH
mIrCl
11.26 s, br
9.30 dt
NH
CHa
A2
ꢀ15.17 s
JHH = 16.5
JPH = 2.0
5.95 d
CHb
JHH = 16.5
7.63 s, br
7.04 s, br
5.90 t
H5 pz
H3 pz
H4 pz
7b
IrCl2{CH@C(H)-p-tolyl}(Hpz)(PPh3)2
3315 m
mNH
11.25 s, br
9.15 dt
JHH = 16.5
NH
CHa
A2
ꢀ15.76 s
(continued on next page)

1018
G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
Table 2 (continued)
Compound
IRa m (cmꢀ1
)
Assgnt
1H NMRb d (J, Hz)
Assgnt
Spin system
31P{1H}NMRb,c
d (J, Hz)
JPH = 2.0
5.87 d
CHb
JHH = 16.5
7.61 s, br
7.02 d
5.89 t
2.26 s
H5 pz
H3 pz
H4 pz
CH3
7c
IrCl2{CH@C(H)COOMe}(Hpz)(PPh3)2
3300 m
1696 s
mNH
mCO
11.13 s, br
10.90 dt
JHH = 16.0
JPH = 2.0
5.60 d
NH
CHa
A2
ꢀ13.97 s
CHb
JHH = 16.0
7.64 s, br
7.03 s, br
5.89 t
H5 pz
H3 pz
H4 pz
CH3
3.48 s
8a
IrCl2{CH@C(H)Ph}(H-3-Mepz)(PPh3)2
3311 m
mNH
10.57 s, br
9.34 dt
NH
CHa
A2
ꢀ16.08 s
JHH = 16.5
JPH = 2.0
5.94 d
CHb
JHH = 16.5
7.47 s, br
5.58 s, br
1.89 s
H5 pz
H4 pz
CH3
9a
IrCl2{CH@C(H)Ph}(Hpz)(PiPr3)2
3267 s
mNH
12.20 br
8.59 dt
NH
CHa
A2
6.33 s
JHH = 12.0
JPH 6 0.5
8.23 d
7.63 d
6.42 t
H5 pz
H3 pz
H4 pz
CHb
5.97 d
JHH = 12.0
2.74 m
1.27 m
CH phos
CH3
10a
IrCl2{CH@C(H)Ph}(HIm)(PPh3)2
3402 m
321 m
mNH
mIrCl
9.31 dt
CHa
A2
ꢀ14.59 s
JHH = 16.5
JPH = 3.8
8.84 s
NH
5.88 d
CHb
JHH = 16.5
7.58 d
7.21 t
H2 Im
H4 Im
H5 Im
6.41 dt
10b
IrCl2{CH@C(H)p-tolyl}(HIm)(PPh3)2
3404 m
mNH
9.17 dt
CHa
A2
ꢀ14.79 s
JHH = 16.5
JPH = 3.8
8.91 s, br
5.84 d
NH
CHb
JHH = 16.5
7.62 d
7.25 t
6.39 dt
2.27 s
H2 Im
H4 Im
H5 Im
CH3
a
b
c
In KBr pellets.
In CD2Cl2 at 25 ꢁC, unless otherwise noted.
Positive shift downfield from 85% H3PO4.

G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
1019
Table 3
of CH3CN and a triplet at ꢀ21.23 ppm of the hydride
ligand.
13C NMR data for selected iridium complexes
Compound
13C NMRa
d (J, Hz)
Assgnt
The 31P{1H} NMR spectra of the 2,20-bipyridine
[IrHCl(bpy)(PPh3)2]BPh4 (6) complex is an AB multiplet,
in agreement with the magnetic inequivalence of the two
phosphine ligands. As a result, the hydride signal appear
in the proton spectra as an ABX (X = 1H) multiplet which
can be simulated with the parameters reported in Table 2.
The same value of 18 Hz found for the two JPH suggests
that both the phosphines should be in a mutually cis posi-
tion with respect to the hydride ligand. On the basis of
these data, a geometry of the VI type can reasonably be
proposed for the bipyridine 6 derivative (Chart 3).
1b
IrHCl2(H-3-Mepz)(PPh3)2
138–127 m
138.7 s
136.8 s
105.6 s
11.1 s
Ph
C3
C5
C4
CH3
2a
4
[IrHCl(Hpz)2(PPh3) 2]BPh4
IrHCl2(HIm)(PPh3)2
165–122 m
144.4 s
131.5 s
Ph
C5
C3
C4
108.8 s
137–127 m
134.2 s
125.8 s
Ph
C2 Im
C4 Im
C5 Im
3.2. Reactivity
114.5 s
Reactivity studies of the new hydride containing N-
donor ligands has been undertaken toward both proton-
ation and insertion reactions, with the aim to test how
the introduction of nitrogenous ligands changes the prop-
erties of hydride complexes.
7a
IrCl2{CH@C(H)Ph}(Hpz)(PPh3)2
141–124 m
137.2 t
139.2 s
124.5 s
113.4 t
Ph
Cb
C5 pz
C3 pz
Cab
JCP = 10
107.2 s
Neutral pyrazole IrHCl2(HRpz)(PPh3)2 (1) and imidaz-
ole IrHCl2(HIm)(PPh3)2 (4) complexes react with Brønsted
acids such as CF3SO3H or HBF4 Æ Et2O to give a pale-
yellow solution from which no stable compound was
isolated. The reaction, however, was studied by NMR
spectroscopy between +20 and ꢀ80 ꢁC and the results
show that the addition of acid at ꢀ80 ꢁC caused a variation
in the proton spectra, with the disappearance of the
hydride triplet near ꢀ20 ppm of the precursors 1 and 4
and the appearance of a new triplet near ꢀ16 ppm. T1 mea-
surements at ꢀ80 ꢁC on this new signal give values of about
120 ms which are comparable with those of the precursors
(between 140 and 120 ms) thus excluding the formation of
a dihydrogen [Ir]-g2-H2 complex [23]. The addition of acid
C4 pz
8a
IrCl2{CH@C(H)Ph}(H-3-Mepz)(PPh3)2
141–124 m
139.5 s
137.0 t
134.7 s
JCP = 4
113.6 t
JCP = 10
106.6 s
11.1 s
Ph
C5 pz
Cb
C3 pz
Ca
C4 pz
CH3
10a
IrCl2{CH@C(H)Ph}(HIm)(PPh3)2
141–127 m
137.3 t
JCP = 4.2
111.5 t
JCP = 10.6
137.0 s
128.3 s
Ph
Cb
Ca
C2 Im
C4 Im
C5 Im
115.0 s
a
CH3
In CD2Cl2 at 25 ꢁC, unless otherwise noted.
JCH = 140 Hz.
P
Ir
P
Ir
C
b
H
N
N
N
Cl
Cl
2203 cmꢀ1 attributed to mCN of the nitrile ligand, while no
absorption attributable to mIrH of the hydride was
observed. The presence of both the nitrile and the hydride
ligands, however, is confirmed by the proton NMR spec-
tra, which show a singlet at 1.24 ppm of the methyl group
Cl
Cl
H
H
P
P
(IV)
(V)
Chart 2.
+
+
H
P
Ir
P
H
N
N
N
N
Cl
N
Cl
H
P
N
N
H
Ir
Ir
H
H
N
Cl
N
N
H
P
P
P
Cl
H
( I )
( II )
( III )
Chart 1.

1020
G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
complexes in refluxing 1,2-dichloroethane to give the corre-
sponding vinyl [Ir]-CH@C(H)R1 (7–10) derivatives, which
were isolated and characterised (Scheme 8).
+
P
Ir
H
P
N
The reaction with alkyne was studied extensively and the
results show that the insertion reaction is very slow at room
temperature and needs reflux conditions in 1,2-dichloroeth-
ane to yield the final vinyl complex in reasonable quanti-
ties. With the tert-butylacetylene, however, the reaction is
so slow that only traces of the vinyl complex were obtained.
The reactivity studies also show that only with the neutral
complexes the reaction proceeds, while with the cationic
[IrHCl(HRpz)2(PPh3)2]+ (2) and [IrHCl(bpy)(PPh3)2]+ (6)
derivatives no vinyl complex was obtained. In these cases,
the hydride precursors were recovered unchanged after sev-
eral hours of reflux with an excess of acetylene. This unre-
activity may be explained by taking into account that the
mechanism proposed [25] for the insertion of alkyne into
the Ir–H bond usually requires a vacant cis site to accom-
modate the alkyne. Whereas in the neutral complexes 1, 4
one of the two chlorides is labile (see Scheme 1) and can
be replaced by the alkyne, allowing the coordination of
R1C„CH prior the insertion, in the cationic 2, 6 no ligand
is probably labile, thus preventing the coordination of the
alkyne and therefore the insertion.
The need of an open coordination site for the insertion
of alkyne into the Ir–H bond prompted us to also study
the reactivity of the pentacoordinate IrHCl2(PPh3)2
obtained from the protonation reaction of pyrazole and
imidazole complexes 1, 4 with alkyne. The reaction was
carried out by adding first an equimolar amount of
HBF4 Æ Et2O and then an excess of terminal alkyne to the
starting IrHCl2(HRpz)(PPh3)2 and IrHCl2(HIm)(PPh3)2
complexes. Surprisingly, no vinyl complex was isolated
from the reaction, which gives a yellow-orange solid char-
acterised as the alkyl-carbonyl IrCl2(g1-CH2C6H5)(CO)-
(PPh3)2 derivative [10] in the case of phenylacetylene.
With tert-butylacetylene, instead, the acyl IrCl2{g1-
C(O)CH2C(CH3)3}(PPh3)2 complex [10] was obtained, as
shown in Scheme 9.
N
Cl
(VI)
Chart 3.
to IrHCl2(HRpz)(PPh3)2 also causes the disappearance of
the signals of the coordinate Hpz and the concurrent
appearance of new signals, attributable to the pyrazole
and imidazole species. These results suggest that the pro-
tonation of pyrazole and imidazole complexes 1, 4 pro-
ceeds to the azolic nitrogen atom of the N-donor ligand,
resulting in the loss of the same ligand and the formation
of the pentacoordinate IrHCl2(PPh3)2 species, as shown
in Scheme 6.
Support for this hypothesis comes from the reversibility
of the reaction which gives the starting 1, 4 complexes
through the addition of base (NEt3) to the solution of
the protonated compounds. Unfortunately, the pentacoor-
dinate IrHCl2(PPh3)2 species is unstable and cannot be iso-
lated in the solid state. However, chemical and
spectroscopic data strongly support the reaction of Scheme
6 for the protonation of the pyrazole 1 and imidazole 4
complexes.
Aryldiazonium cations ArNþ2 do not react with the 1–6
hydrides containing nitrogenous ligands and the starting
complexes can be recovered unchanged after several hours
of reaction (Scheme 7).
This unreactivity is somewhat unexpected because the
comparable IrHCl2L(PPh3)2 [L = P(OEt)3 and PPh(OEt)2]
complexes [24] do react with aryldiazonium cations to give
the corresponding [Ir]-HN=NAr aryldiazene derivatives.
The introduction of a N-donor ligand such as pyrazole,
imidazole or CH3CN into the coordination sphere of
[IrHCl2(PPh3)2] hydridic fragment changes the properties
of the corresponding Ir–H bond, making it unreactive
toward the insertion of an ArNþ2 group.
The reaction proceeds with the hydrolysis of the coordi-
nate alkyne to give the alkyl-carbonyl 12 or the acyl 11
derivatives and these results are the same as those we pre-
viously obtained [10] from the reaction of IrHCl2(PPh3)3
with alkynes. As in the previous cases, the traces of water
present in the solvent are enough to afford the final
complexes. The hydrolysis of the alkyne with C„C bond
Terminal alkynes such as R1C„CH (R1 = Ph, p-tolyl,
COOCH3), instead, react with pyrazole and imidazole
+H+
IrHCl2(Hpz)(PPh3)2
[IrHCl2(PPh3)2] + H2pz+
-H+
1
R1C≡CH
IrHCl2(HRpz)(PPh3)2
IrCl2{C(H)=C(H)R1}(HRpz)(PPh3)2
+H+
-H+
IrHCl2(HIm)(PPh3)2
[IrHCl2(PPh3)2] + H2Im+
1
7, 8
4
R1C≡CH
R1C≡CH
Scheme 6.
IrHCl2(HRpz)(PiPr3)2
IrCl2{C(H)=C(H)R1}(HRpz)(PiPr3)2
3
9
+
IrHCl2(HIm)(PPh3)2
IrCl2{C(H)=C(H)R1}(HIm)(PPh3)2
[Ir]–H + ArN2
1-6
4
10
Scheme 7.
Scheme 8. R1 = Ph, a; p-tolyl, b; CH3COO, c.

G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
1021
exc. HC≡CPh
IrHCl2(HRpz)(PPh3)2
IrHCl2(HIm)(PPh3)2
IrCl2(η1-CH2C6H5)(CO)(PPh3)2
H2O
12
HBF4
IrHCl2(PPh3)2
exc. HC≡CC(CH3)3
IrCl2{η1-C(O)CH2C(CH3)3}(PPh3)2
.
H2O
11
Scheme 9.
cleavage and formation of alkyl or acyl complexes in the
reaction of pentacoordinate IrHCl2(PPh3)2 species is there-
fore not surprising taking into account the behaviour of the
hexacoordinate IrHCl2(PPh3)3 complex containing one
labile PPh3 ligand [10]. In both cases the reaction with
alkyne probably gives the IrHCl2(g1-R1C„CH)(PPh3)2
intermediate which results to be the first step of the hydro-
lysis affording the final 12 or 11 derivatives.
The vinyl complexes IrCl2{CH@C(H)R1}(HRpz)P2
(7–9) (P = PPh3, PiPr3) and IrCl2{CH@C(H)R1} (HIm)-
(PPh3)2 (10) are red-brown solids stable in air and in a solu-
tion of the most common organic solvents, where they
behave as non-electrolytes. Their characterisation is sup-
ported by analytical and spectroscopic data (Tables 2 and
3) and by the crystal structure determination of the
IrCl2{CH@C(H)Ph}(Hpz)(PPh3)2 (7a) derivative.
The solid-state structure of trans-E-[IrCl2{CH@C(H)-
Ph}(Hpz)(PPh3)2] (7a) was determined by single-crystal
X-ray crystallographic analysis (Table 1). ORTEP plot,
including the atom-numbering scheme, of the complex is
shown in Fig. 1. Selected bond lengths and bond angles of
the complex are listed in Table 4. The iridium atom is coor-
dinated by two triphenylphosphine ligands, two chlorine
atoms, one pyrazolyl ligand and a phenylvinyl ligand in
an octahedral fashion. The geometry of the complex can
be rationalised as a distorted octahedron with the two phos-
phorus atoms of the triphenylphosphine ligands occupying
the apical positions, in relative trans positions [P(1)–Ir–
P(2) = 171.09(4)ꢁ]. The equatorial plane is formed by the
two chlorine atoms mutually trans disposed [Cl(1)–Ir–
Cl(2) = 172.59(4)ꢁ] and the carbon atom of the styryl ligand
and the nitrogen atom of a pyrazolyl ligand also in relative
trans positions [C(1)–Ir–N(1) = 177.30(17)ꢁ]. These trans
angle values show some distortion in the defined as equato-
rial plane since the chlorine atoms are deviated in the direc-
tion of the pyrazolyl ligand and the phosphorous atoms are
deviated in the direction of the styrene ligand.
The pyrazolyl ligand is situated almost in the defined as
equatorial plane [dihedral angle 4.0(4)ꢁ]. This disposition
allows intramolecular hydrogen bonds between the coordi-
nated chlorine atoms and the ortho atoms of the ring, N(2)
and C(73) (see Table 5). The styryl ligand, however, is devi-
ated from the equatorial plane showing more twisting free-
dom along the Ir–C(1) and C(2)–C3(3) bonds. The carbon
˚
atom labelled as C(2) lies only 0.165(6) A out of the plane
defined as equatorial for the complex, but the donor car-
˚
bon atom labelled as C(1) lies 0.547(8) A out of the plane
of the benzene ring. The benzene ring plane forms a dihe-
dral angle of 36.6(1)ꢁ with the defined as equatorial plane
for the complex.
Distances and angles into the ligands are as expected
˚
since values of 1.309(6) A for C(1)–C(2) and of 1.485(6)
A for C(2)–C(3) are characteristic for a styryl ligand as well
C6
C7
˚
C5
as the sp2 nature of the C(1) and C(2) atoms [26]. The two
substituents at the double bond of the styrene ligand are in
trans positions (E-isomer) as is usual for these kinds of
complexes, although some cis compounds (Z-isomer) could
be found [27].
C8
C3
C55
C54
C56
C2
The phenyl rings at the phosphine ligands are in a stag-
gered disposition with each other as is seen by the torsion
angle values close to 60ꢁ of C–P–P–C (see Table 4), show-
ing no distortion at this stage.
The IR spectra of all the vinyl complexes 7–10 show a
medium-intensity band at 3402–3267 cmꢀ1 attributed to
the mNH of the HRpz or HIm ligand. In the spectra of
the IrCl2{CH@C(H)COOCH3}(Hpz)(PPh3)2 (7c) complex
a strong band at 1696 cmꢀ1 is also present, due to mCO of
the COOCH3 substituent.
C53
Cl2
C1
Ir
C51
C52
P2
P1
C46
C11
C41
C45
Cl1
C16
C15
C12
C13
N1
C44
N2
C43
C73
C14
C71
The 1H NMR spectra show, beside the signals of the N-
and P-donor ligands, a doublet of triplets between 10.90
and 8.59 ppm attributed to the Ha proton of the vinyl
ligand. The Hb proton signal, instead, appear as a doublet
between 5.97 and 5.60 ppm and these attributions are
C72
Fig. 1. Molecular structure of trans-E-[IrCl2{CH@C(H)Ph}(HPz)(PPh3)2]
(7a).

1022
G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
Table 4
˚
Bond lengths (A) and angles (ꢁ) for [IrCl2{CH@C(H)Ph}(Hpz)(PPh3)2] (7a)
Lengths
Ir–C(1)
Ir–Cl(1)
2.042(4)
2.3534(10)
2.3865(12)
1.830(4)
1.857(4)
1.848(4)
1.309(6)
1.378(6)
1.379(6)
1.372(6)
1.322(5)
1.362(7)
Ir–N(1)
Ir–Cl(2)
Ir–P(1)
2.192(4)
2.3841(10)
2.3986(11)
1.832(4)
1.834(4)
1.852(5)
1.485(6)
1.386(6)
1.370(7)
1.368(6)
1.356(5)
1.340(8)
Ir–P(2)
P(1)–C(21)
P(1)–C(31)
P(2)–C(41)
C(1)–C(2)
C(3)–C(8)
C(4)–C(5)
C(6)–C(7)
N(1)–C(73)
N(2)–C(71)
P(1)–C(11)
P(2)–C(61)
P(2)–C(51)
C(2)–C(3)
C(3)–C(4)
C(5)–C(6)
C(7)–C(8)
N(1)–N(2)
C(71)–C(72)
Angles
C(1)–Ir–N(1)
N(1)–Ir–Cl(1)
N(1)–Ir–Cl(2)
C(1)–Ir–P(2)
Cl(1)–Ir–P(2)
C(1)–Ir–P(1)
Cl(1)–Ir–P(1)
P(2)–Ir–P(1)
N(2)–N(1)–Ir
C(72)–C(71)–N(2)
177.30(17)
86.07(10)
86.54(10)
85.93(11)
91.76(4)
85.77(11)
85.98(4)
171.09(4)
124.7(3)
C(1)–Ir–Cl(1)
C(1)–Ir–Cl(2)
Cl(1)–Ir–Cl(2)
N(1)–Ir–P(2)
Cl(2)–Ir–P(2)
N(1)–Ir–P(1)
Cl(2)–Ir–P(1)
C(2)–C(1)–Ir
N(1)–N(2)–C(71)
N(1)–C(73)–C(72)
96.54(13)
90.86(13)
172.59(4)
94.70(10)
88.33(4)
93.74(10)
95.02(4)
134.1(4)
110.0(5)
110.3(5)
107.1(6)
Torsion angles
Ir–C(1)–C(2)–C(3)
C(21)–P(1)–P(2)–C(51)
C(11)–P(1)–P(2)–C(61)
C(31)–P(1)–P(2)–C(61)
C(21)–P(1)–P(2)–C(41)
ꢀ176.9(3)
56.8(2)
C(11)–P(1)–P(2)–C(51)
C(31)–P(1)–P(2)–C(51)
C(21)–P(1)–P(2)–C(61)
C(11)–P(1)–P(2)–C(41)
C(31)–P(1)–P(2)–C(41)
ꢀ179.5(2)
ꢀ59.5(2)
170.7(2)
60.0(2)
ꢀ65.6(2)
54.5(2)
ꢀ63.7(2)
ꢀ180.0(2)
Table 5
(JCP = 10.0 Hz) attributed to the Ca carbon resonance.
The HMQC and HMBC experiments confirm the attribu-
tion showing the correlation between the triplet at 113–
111 ppm in the 13C spectra with the proton signals at
10.90–8.59 ppm of the Ha vinyl resonance. The 13C signal
near 137 ppm, instead, is correlated to the signal at 5.97–
5.60 ppm of the Hb vinyl proton, in agreement with the
proposed assignment for the signals.
The IR spectra of the vinyl complexes 7a and 10a show,
in the far region, only one band at 324 cmꢀ1 (7a) and
321 cmꢀ1 (10) attributable to the stretching of the IrCl
bond, in agreement with the mutually trans position of
the two chloride ligands. On the basis of these data, a
trans–trans geometry of the VII type, exactly like that
observed in the solid state, can be proposed for the
IrCl2{CH@C(H)R1}LP2 (7–10) (L = HRpz, HIm;
P = PPh3, PiPr3) vinyl derivatives (Chart 4).
Hydrogen bonds parameters for [IrCl2{CH@C(H)Ph}(Hpz)(PPh3)2] (7a)
˚
(A, ꢁ)
D–H. . .A
d(D–H)
d(H. . .A)
d(D. . .A)
\(DHA)
N(2)–H(21). . .Cl(2)
C(73)–H(73). . .Cl(1)
C(12)–H(12). . .N(2)
C(32)–H(32). . .Cl(1)
C(42)–H(42). . .N(1)
C(56)–H(56). . .Cl(2)
C(54)–H(54). . .Cl(10)
C(71)–H(71). . .Cl(200)
C(8)–H(8). . .Cg
0.86
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
2.57
2.66
2.60
2.56
2.55
2.66
2.71
2.82
3.03
3.094(5)
3.162(5)
3.280(6)
3.327(4)
3.213(6)
3.485(5)
3.439(5)
3.597(6)
3.833(4)
120.4
115.0
130.2
140.6
128.6
148.3
136.0
141.6
145.4
Cg stands for the centroid of the benzene ring labeled as C(51)–C(56).
0
Symmetry transformations used to generate equivalent atoms: : x + 1, y,
z; 00: 1 ꢀ x, 1 ꢀ y, ꢀz.
confirmed by a COSY experiment. Taking into account
that the 31P{1H} NMR indicate the magnetic equivalence
of the two phosphine ligands showing a sharp singlet
between ꢀ16.08 and 6.33 ppm, the vinyl Ha proton signal
can be easily simulated using an ABX2 (A = 1Ha, B = 1Hb,
X2 = 31P) model with JAB near 16 Hz and JAX of about
2 Hz. The values of the coupling constant JHH of 16 Hz
also suggest [28] a trans arrangement of the two vinyl pro-
tons, as observed in the solid state.
Hα
P
Cα
R
Cl
Cβ
Hβ
Ir
Cl
L
P
(VII)
The 13C NMR spectra (Table 3) confirm the presence of
the vinyl ligand showing a triplet at 113.6–111.5 ppm
Chart 4.

G. Albertin et al. / Journal of Organometallic Chemistry 691 (2006) 1012–1024
1023
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4. Conclusions
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The synthesis of a series of neutral and cationic hydride
complexes of iridium(III) containing N-donor ligands such
as pyrazole, imidazole and 2,20-bipyridine has been
achieved using IrHCl2(PPh3)3 as a precursor. Protonation
of the azole complexes IrHCl2L(PPh3) (L = HRpz, HIm)
with Brønsted acids does not give any g2-H2 species, but
proceeds with the loss of the nitrogenous ligand and forma-
tion of the unstable pentacoordinate IrHCl2(PPh3)2 deriva-
tive. Among the properties shown by the new hydride
complexes, the facile insertion of terminal alkyne into the
Ir–H bond to give a series of stable and isolable
vinyl IrCl2{CH@C(H)R1}L(PPh3)2 derivatives can be
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Acknowledgements
The financial support of MIUR (Rome) – PRIN 2004 –
is gratefully acknowledged. We thank Daniela Baldan for
technical assistance.
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