Synthesis and some reactivity of cationic alkyl nitrosyl iridium(III) derivatives

Article abstract of DOI:10.1016/S0022-328X(99)00096-0

The iridium(III) dimethyl derivatives [Ir(Me)₂Cp*(L)] (Cp* = η⁵-C₅Me₅; L = PPh₃ (1a), PMePh₂ (1b), PMe₂Ph (1c), PMe₃ (1d)) react with NOBF₄ in CH₂

Full text of DOI:10.1016/S0022-328X(99)00096-0

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 73–86
Synthesis and some reactivity of cationic alkyl nitrosyl iridium(III)
derivatives
Pietro Diversi a,*, Fabrizia Fabrizi de Biani b, Giovanni Ingrosso a, Franco Laschi b,
Antonio Lucherini a, Calogero Pinzino c, Piero Zanello b
a Dipartimento di Chimica e Chimica Industriale dell’Uni6ersita` di Pisa, 6ia Risorgimento 35, I-56126 Pisa, Italy
b Dipartimento di Chimica, Uni6ersita` di Siena, Pian dei Mantellini 44, I-53100 Siena, Italy
c Istituto di Chimica Quantistica ed Energetica Molecolare del CNR, 6ia Risorgimento 35, I-56126 Pisa, Italy
Received 4 December 1998; received in revised form 9 February 1999
Abstract
The iridium(III) dimethyl derivatives [Ir(Me)2Cp*(L)] (Cp*=h5-C5Me5; L=PPh3 (1a), PMePh2 (1b), PMe2Ph (1c), PMe3 (1d))
react with NOBF4 in CH2Cl2 to give the iridium(III) cationic alkylnitrosyl derivatives [Ir(Me)2Cp*(NO)]BF4 (2), and
[Ir(Me)Cp*(NO)(L)](BF4)2 (L=PMePh2 4b, PMe2Ph 4c, PMe3 4d). EPR spectroscopy shows that the reaction proceeds through
the iridium(IV) intermediates 1a+ –1d+. Treatment of 1d with NOBF4 in acetonitrile gives, in addition to 4d, the acetonitrile
substitution products [Ir(Me)Cp*(CH3CN)(PMe3)]BF4 (5d) and [IrCp*(CH3CN)2(PMe3)](BF4)2 (6d). Electrochemical and chemi-
cal reduction of 4b–4d afford the corresponding [Ir(Me)Cp*(NO)(L)](BF4) 7b–7d, which have been studied by EPR spectroscopy.
Reaction of
2 with PPh3 gives [Ir(Me)2Cp*(PPh3)]; treatment of 4b and 4c with the appropriate phosphine gives
[Ir(Me)Cp*(L)2](BF4) (L=PMePh2, PMe2Ph), respectively. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Nitrosyls; Iridium; Electrochemistry; EPR
congeners. Moreover the above nitrosyl derivatives
1. Introduction
have been found to undergo an unprecedented NO+
substitution reaction by treatment with acetonitrile and
phosphines. Part of this study has been published in
preliminary form [2].
The iridium(III) dimethyl derivatives [Ir(Me)2Cp*(L)]
(Cp*=h5-C5Me5; L=PPh3 (1a), PMePh2 (1b),
PMe2Ph (1c), PMe3 (1d)) are able to activate aromatic
C-H bonds under electron transfer conditions [1]. In the
course of an extensive investigation on the redox be-
haviour of the above systems in the presence of various
one-electron oxidants, we have studied the reaction of
1a–1d with NOBF4 which affords interesting cationic
alkylnitrosyl derivatives. In this paper we present the
synthesis and characterization of these nitrosyl deriva-
tives of formula [Ir(Me)2Cp*(NO)]BF4 (2), and
[Ir(Me)Cp*(NO)(L)](BF4)2 (L=PMePh2 (4b), PMe2Ph
(4c), PMe3 (4d)), along with a study of their reactivity
towards reduction and displacement reactions. Electro-
chemical and chemical studies showed that the above
dicationic iridium(III) complexes undergo sequential
one-electron reductions to the corresponding neutral
2. Results and discussion
2.1. Reaction of the iridium(III) dimethyl deri6ati6es
[Ir(Me)2Cp*(L)] (1a–1d) with NOBF4 in
dichloromethane
The reaction of 1a–1d with NOBF4 was studied by
EPR spectroscopy, carrying out the reaction in the
cavity of the spectrometer. The resulting one-electron
oxidation products 1a+ –1d+ have been detected at
183 K where single line spectra in solution at g=1.931
(1a+), 1.939 (1b+), 1.942 (1c+) and 1.943 (1d+) are
observed. By lowering the temperature down to 113–
123 K, the spectra appear as structured signals, as
shown in Fig. 1 for 1b+ –1d+, while raising the temper-
ature causes the signals to disappear gradually.
* Corresponding author. Tel.: +39-5-918225; fax: +39-50-918260.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00096-0

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P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
Fig. 1. EPR spectra of the species deriving from the reaction of Ir(Me)2Cp*(L) (L=PPh3 (1a), PPh2Me (1b), PPhMe2 (1c), PMe3 (1d)) with
NOBF4 in CH2Cl2. (a) observed spectrum; (b) simulated spectrum.
As already noted [2], the anisotropic spectra implying
metal-centred character could be assigned in first ap-
proximation to an axial EPR symmetry, where the
hyperfine splitting of the perpendicular absorption into
a quartet was attributed to spin-coupling to the iridium
nucleus (191Ir, 37%; 193Ir, 63%: both I=3/2). However
computer simulations by spectral optimization
software1 showed that the spectra of 1a+ –1d+ are
better interpreted as corresponding to rhombic EPR
symmetry (g1"g2"g3; A1"A2"A3; all tensor axes
coincident), where g1 and g2, because of the linewidths
of the resonances, are overlapping (see Fig. 1 and Table
1).
Since the observed hyperfine structure could be due,
alternatively, to the interaction of the unpaired electron
with the three hydrogen nuclei of an iridium bonded
methyl group, we have studied the reaction of Ir(Me-
d3)2(h5-C5Me5)(PMe3) (1d–d6) with NOBF4 under the
same conditions as above. 1d–d+6 has in solution the
same behaviour as the non deuteriated species, showing
a large signal centred at g=1.942, which decreases up
to disappear on raising the temperature. Moreover the
spectrum of 1d–d+6 in the frozen state at 123 K (Fig. 2)
is almost identical to that observed for 1d+ (g1=2.012,
g2=1.979, g3=1.831; A1=19.32, A2=30.55, A3=
24.44 G): this clearly indicates that the unpaired elec-
tron does not interact with the protons of a methyl
ligand.
In order to test such possibility, we have reacted the
isostructural complex of rhodium(III) RhMe2(h5-
C5Me5)(PMe3) with NOBF4. The EPR spectrum of the
resulting oxidation product should present a similar
pattern if the above hypothesis was correct. In contrast,
Table 1
X-band EPR parameters of the 1a+–1d+ species generated by oxida-
a
tion of 1a–1d with NOBF4
Species
g1
g2
g3
A1(G)
A2(G)
A3(G)
1a+
1b+
1c+
1d+
2.067
2.011
2.009
2.013
2.033
1.975
1.977
1.979
1.879
1.830
1.830
1.831
23.46
19.09
20.10
18.08
30.77
30.71
29.60
30.42
26.07
24.01
24.75
22.42
a Spectra recorded at 113 K in the case of 1a+–1d+; at 123 K in
the case of 1b+–1c+
.
Another possibility was that the spectra could be
understood in terms of a rhombic symmetry, the high-
field signal resulting from the superimposition of two
close components, each appearing as doublet because
of the hyperfine interaction with the 31P nucleus (I=1/
2) of the phosphine ligand.
1 The software was provided by the Illinois EPR Research Center,
NIH Division of Research, Resonances Grant. No RR01811.
Fig. 2. EPR spectrum of the species deriving from the reaction of
Ir(CD3)2(h5-C5Me5)(PMe3) (1d–d6) with NOBF4 in CH2Cl2.

P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
75
On raising the temperature, the intensity of the EPR
signals due to 1a+ –1d+ decreases disappearing in the
−30 to 0°C range (depending on the nature of the
phosphine). By carrying out the reaction at room tem-
perature on a preparative scale, different diamagnetic
products are obtained depending on the nature of the
phosphine and of the NO+/Ir ratio.
In the case of 1a by using a NO+/Ir ratio=1 a
mixture
of
the
cationic
nitrosyl
derivative
[Ir(Me)2Cp*(NO)]+ (2) and of the bisphosphino com-
plex [Ir(Me)Cp*(PPh3)2]+ (3a) is formed, and methane
is evolved; under the same conditions 1b, 1c and 1d give
complicated mixtures which contain 2 as shown by
1H-NMR spectroscopy. By using a NO+/Ir ratio=2,
1a gives 2 and only small amounts of 3a; 1b, 1c and 1d
afford the dicationic nitrosyl derivatives [Ir(Me)Cp*-
(NO)(L)]2+ (L=PMePh2 (4b), PMe2Ph (4c), PMe3
(4d)) (Scheme 1).
1
The complexes have been characterized by H-NMR,
Fig. 3. EPR spectrum of the species deriving from the reaction of
Rh(Me)2(h5-C5Me5)(PMe3) (2d) with NOBF4 in CH2Cl2. (a) Ob-
served; (b) simulated spectrum.
IR, MS and carbon and hydrogen elemental analyses.
The identity of 3a was verified by comparison of the
1H-NMR spectrum with that of an authentic sample
prepared by chloride abstraction from [Ir(Me)(Cl)-
Cp*(PPh3)] [3] with AgBF4 in CH2Cl2 in the presence of
PPh3. All the IR spectra of the above nitrosyl com-
plexes show strong NO absorptions at very high fre-
quencies (1909−1843 cm−1), pointing to a linear
Ir–N–O arrangement.
A common feature of these reactions is the in-
tramolecular formation of methane. In fact by reacting
1a–1d with NO+ in deuteriated solvents, CH4 forms
exclusively (l 0.20 in CD2Cl2, l 0.14 in C6D6, l 0.16 in
CD3NO2); moreover the 2H-NMR spectrum of 4d
shows the presence of deuterium on the Cp* ligand
(CD3NO2, l 2.08). Then the loss of methane occurs
intramolecularly and the resulting intermediate (most
since rhodium has nuclear spin 1/2, in case of interac-
tion of the unpaired electron with the metal center the
spectrum should be simpler and quite different from
those observed for the above iridium cations.
This is indeed the case: the spectrum shown in Fig. 3
presents three components, one of these being the sum
of two close doublets resulting from the hyperfine cou-
pling of the electronic spin with the rhodium nucleus.
The parameters obtained by simulation are the follow-
ing: g1=2.018; g2=1.989; g3=1.932; A1=1.37 G;
A2=30.24 G; A3=15.73 G.
Then the hyperfine coupling constants result from the
unpaired electron delocalization on the iridium nucleus,
and the species 1a+ –1d+ can be described as low spin
cationic complexes of iridium(IV).
Scheme 1.

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P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
The 1“3a and 1“4 reactions should occur through
an oxidatively induced cleavage of the Ir–Me bonds
resulting in the formation of methane via the C–H
activation of the Cp* group with subsequent H abstrac-
tion from the solvent, the organometallic fragment
being trapped by the phosphine ligand or the nitrosyl
cation. Accordingly 3a was also obtained by treating 1a
with triphenylphosphine in the presence of a classical
one-electron oxidant like FeCp2+. Then the formation
of 3a and 4 resembles the reaction of 1a–1d [2] with
pyridine in the presence of an oxidant.
Moreover such reactions seem to mimic the mecha-
nistic steps which are at the basis of the activation of
arenes by 1a–1d under electron transfer catalysis,
where, in the absence of better coordinating agents, aryl
radicals deriving from the aromatic solvent enter the
coordination sphere of the metal [1].
2.2. Reactions of [Ir(Me)2Cp*(PMe3)] (1d) with NOBF4
in acetonitrile
Tilset and coworkers [6,7] have studied the oxidation
of 1a and of its rhodium congener in CH3CN by using
Fe(III) complexes. In the case of iridium, methane and
the acetonitrile complex [Ir(Me)Cp*(CH3CN)(PPh3)]+
are the main products [6]. Then it was interesting to
study the reaction of the iridium(III) dimethyl deriva-
tives with NOBF4 in acetonitrile where NO+ and
CH3CN could compete in coordinating to the metal
centre.
Scheme 2.
probably a ‘tucked-in’ species) on its turn abstracts D
from the solvent, as it was already observed for related
reactions of 1a–1d [1c,7].
Treatment of 1d with an equimolar amount of
NOBF4 in CD3CN produces an immediate variation of
colour from light yellow to deep yellow and a vigorous
outcome of CH4 (l 0.19, singlet) along with the forma-
tion of a new organometallic product 5d (Scheme 3).
As for the origin of the nitrosyl derivatives, EPR
spectroscopic evidences are consistent with the forma-
tion of the primary oxidation products 1a+ –1d+ as
the first step. Then, depending on the nature of the
phosphine and on the stoicheiometry, two reaction
patterns are available: the loss of phosphine, followed
by coordination of NO, or the loss of methane followed
by coordination of phosphine or NO+. According to
this picture, the 1“2 reaction should involve the phos-
phine displacement by NO in the transient oxidation
product 1+, rather than the more common phosphine
substitution by NO+ from an 1/NO+ adduct, which
was suggested in the literature [4,5] for similar cases
(Scheme 2).
1
The H-NMR spectrum of the reaction mixture reveals
that the starting substrate was completely consumed
1
after ca. 24 h. The H-NMR spectrum of 5d displays
the presence of one iridium bonded methyl group (dou-
blet at l 0.44, J=6.6 Hz) in addition to the signal of
the Cp* protons (doublet, l 1.73, J=2.1 Hz) and to
the PMe3 resonances (l 1.49, J=10.7 Hz). On this
basis the compound was formulated as the tetrafluobo-
rate salt of [Ir(Me)Cp*(CD3CN)(PMe3)]+, which was
also prepared by an alternative route by reaction of
[Ir(Me)(Cl)Cp*(PMe3)] with AgBF4 in CD3CN.
Scheme 3.

P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
77
only 5d and 6d are present (in a 1/1 ratio). These data
suggest that 5d and 6d are formed from 4d by reaction
with acetonitrile (since formation of ethane was not
observed it is quite improbable that 6d is a primary
oxidation product [6,7]).
In order to verify this hypothesis we have studied the
reactions of isolated 4d with acetonitrile.
1H-NMR spectroscopy shows the slow (10 days) and
complete conversion of 4d into a mixture of 5d and 6d,
the latter being the major product (1:5) (Scheme 5).
The formation of 5d and 6d is interesting since
substitution reactions of the nitrosyl ligand are not
frequently observed [9]. For instance when both the
nitrosyl and carbonyl ligands are present, CO rather
than NO is substituted: this is consistent with a
stronger M–NO bond compared to the M–CO bond
because of the greater backbonding degree of NO [10].
Moreover, as far as we know, cases where the nitrosyl
ligand comes out as NO+ are unknown, and the reason
of the unusual behaviour of 4d is to be attributed to the
particularly low Ir–NO bond energy (as inferred from
the extremely high value of the NO stretching) being
part of a doubly charged complex cation.
Scheme 4.
Then the reaction is substantially analogous to the
oxidation of 1a with ferrocenium in acetonitrile de-
scribed in the literature [7].
Treatment of 1d with an excess of NOBF4 (NO+/
Ir=2) in CD3CN, causes the colour to change from
1
yellow to deep maroon. The H-NMR spectrum soon
after the mixing of the reagents shows that, in addition
to CH4 and 5d, [Ir(Me)Cp*(NO)(PMe3)](BF4)2 (4d) and
[IrCp*(CD3CN)2(PMe3)](BF4)2
The reaction of 4b with CD3CN gives quantitatively
after 4 days [IrCp*(CD3CN)2(PMePh2)]2+ (6b), as
shown by the formation in the NMR spectrum of two
new doublets due to Cp* (l 1.61, J=2.2 Hz) and to
PMePh2 (l 2.45, J=10.7 Hz). Identification of 6b was
(6d)
are
formed
1
(Scheme 4). Complex 6d was identified by its H-NMR
spectrum showing a doublet due to the Cp* protons (l
1.79, J=2.3 Hz) and a doublet due to PMe3 (l 1.74,
J=11.8 Hz), in fair agreement with the data reported
in the literature for the triflate salt of the same cation
[8]. Finally 6d was independently prepared by reaction
of [Ir(Cl)2Cp*(PMe3)] with an excess of AgBF4 in
CD3CN.
1
definitely accomplished by comparison of its H-NMR
data with those of an authentic sample obtained by
reaction of [IrCl2Cp*(PMePh2)] with an excess of
AgBF4 in CD3CN. In contrast with 4d no replacement
of NO+ by acetonitrile occurs.
Complexes 4d, 5d and 6d are initially produced in
almost equal amounts, but during the reaction 4d
slowly decreases in favour of 5d and 6d; after 7 days
The reactions of both 4b and 4d with acetonitrile to
give 6b and 6d imply the loss of Me and NO from the
coordination sphere. Although we have not been able
Scheme 5.

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P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
1.00 V s−1 shows that: (i) the current function ipc/61/2
remains substantially constant; (ii) the current ratio
ipa/ipc is constantly equal to 1; (iii) the peak-to-peak
separation progressively increases from 65 to 98 mV.
These data are representative of a chemically and essen-
tially electrochemically reversible one-electron process.
Since the formal electrode reduction of the couple
NO+/NO occurs at quite higher potential values (E°%
ca. +1.4 V) [13] and in spite of the hard-to-assign
nature of redox processes exhibited by metal-NO com-
plexes (see for instance [14]), we preliminarily attribute
the reduction process to the iridium(III)/(II) couple,
demanding the exact nature of the reduction to the
below discussed EPR responses.
Controlled potential coulometry in correspondence
to the first reduction step (Ew= +0.2 V) consumes one
electron/molecule. In confirmation of the chemical re-
versibility of the first cathodic step, the solution result-
ing from exhaustive one-electron reduction exhibits a
cyclic voltammetric profile quite complementary to the
original one. By contrast, the further one-electron re-
duction at the second cathodic step (Ew= −0.4 V)
affords a solution which no more exhibits peak-systems
related to the original ones.
Fig. 4. Cyclic voltammograms recorded at a platinum electrode in
solution of 4d (1.1×10−3 mol dm−3) in acetone and [NBu4][ClO4]
(0.2 mol dm−3). Scan rates: (top) 0.1 V s−1; (bottom) 5.12 V s−1
.
to establish the fate of these ligands, a plausible hy-
pothesis is the formation of MeNO, which could even-
tually dimerize or isomerize [11].
Then the facts concerning the reaction of 1d with
NO+ in acetonitrile may be summarized as following:
when equimolar amounts are used, NO+ behaves as a
one-electron oxidant and the acetonitrile complex
[Ir(Me)Cp*(MeCN)(PMe3)]+ (5d) forms, as in the case
of the Tilset paper [6]; when two equivalents of NO+
are used, the excess of NO+ acts as the preferred ligand
to give 4d, which slowly undergoes formal substitution
of NO+ or MeNO by the acetonitrile solvent to afford
5d and 6d respectively.
The formal electrode potentials of the iridium(III)/
(II)/(I) redox changes exhibited by the present com-
plexes are compiled in Table 2. The Ir(III)/Ir(II) redox
potentials of these complexes follow the electronic ef-
fects expected on the basis of the content of methyl
groups in the phosphine ligand. This is consistent with
the increasing phosphine basicity (pKa: 4.57 PMePh2;
6.50 PMe2Ph; 8.65 PMe3) [15], which makes the iridium
system having the aliphatic phosphine less prone to
reduction.
In all cases the corresponding iridium(II) complexes
are relatively stable. In comparison the related rheni-
um(I) complex [Re(Me)Cp(NO)(PPh3)] undergoes a
one-electron oxidation process to the corresponding
rhenium(II) congener, which is complicated by chemical
reactions [16].
It is also interesting to compare the redox behaviour
of the iridium(III) nitrosyl complexes with those of the
corresponding complexes 1b, 1c and 1d, in which the
nitrosyl group is replaced by a methyl group. As a
proof of the strong electronic effects played by the
nitrosyl group, 1b, 1c and 1d only undergo one electron
oxidation to the corresponding iridium(IV) congeners
[1].
2.3. Reduction of nitrosyl iridium(III) deri6ati6es [Ir
(Me)Cp*(NO)(L)](BF4)2 (L=PMePh2 4b, PMe2Ph 4c,
PMe3 4d)
2.3.1. Electrochemical reduction
As a typical example of the electrochemical be-
haviour of the present nitrosyl complexes, Fig. 4 shows
the cyclic voltammetric response exhibited by 4d in
acetone solution.
Two subsequent reduction processes appear, the first
of which has features of chemical reversibility, whereas
the second one is complicated by slow chemical reac-
tions. Only at high scan rates no spurious peaks associ-
ated to the second cathodic step are present.
Analysis [12] of the cyclic voltammograms relative to
the first reduction with scan rates varying from 0.02 to
Because of the chemical stability of the one-electron
reduced complexes, EPR measurements on their ex-

P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
79
Table 2
Formal electrode potentials (V vs. SCE) and peak-to-peak separations (mV) for the redox changes exhibited by the present iridium(III) alkyl
complexes
IV/III
III/II
a
II/I
a
Complex
E°%
DEp
E°%
DEp
E°%
DEp
Solvent
Ir
Ir
Ir
4b
4c
4d
1b
1c
1d
+0.62
+0.59
+0.55
90
81
80
−0.17
−0.08
−0.22
80
90
80
Me2CO
Me2CO
Me2CO
CH2Cl2
CH2Cl2
CH2Cl2
+0.36
+0.30
+0.28
80 a
120 b
114 b
a Measured at 0.2 V s−1
b Measured at 1 V s−1 see Ref. [1c]).
.
vent in the electrochemical route (acetone), which can
act as a better coordinating agent than CH2Cl2.
haustive one-electron reduced solutions have been per-
formed in order to ascertain the metallic character of
the relevant cathodic steps.
Table 3 reports the temperature dependent X-band
EPR parameters relevant to the species 7b–7d obtained
by electrochemical reduction of 4b–4d. The EPR
parameters are obtained by computer simulation of the
experimental temperature dependent spectra [17]. It is
to be noted that all the S=1/2 paramagnetic monoca-
tions display completely reversible magnetic behaviour
in the experimental temperature range (T=100–285
K). Fig. 5 shows the X-band EPR spectra of the
monocation electrogenerated from 4c, the upper one
being recorded at 100 K, the lower one at room temper-
ature. The glassy lineshape is characteristic of a metal-
in-character rhombic structure displaying minor
spectral resolution in the low-field region; the room-
temperature spectrum is unresolved, due to actual
DHiso\ of the relevant metal Aiso hyperfine splittings
(B40 G).
2.3.2. Chemical reduction
The values of the potentials reported in Table 2
indicate that the relatively stable one-electron reduction
By comparison of the actual experimental data of the
monocations obtained from 4b–4d with those relevant
to the analogous compounds obtained by chemical
synthesis (Table 4), it is evident the good agreement
between the corresponding paramagnetic parameters,
even in the presence of some differences, particularly
evident in the case of the species which has been
electrogenerated from 4d. This behaviour is not surpris-
ing [1] by considering the different synthesis pathways
and, in particular, the non-innocent nature of the sol-
Fig. 5. X-band EPR spectra of the electrogenerated 7c species. (Top)
Liquid nitrogen temperature; (bottom) room temperature.
Table 3
Temperature-dependent X-band EPR parameters of the electrogenerated species 7b–7d a
b,c
b
b
d
Species
g1
g2
g3
Bg\ b
A1 (G) b
A2(G) b
A3(G) b
BA\(G) b
giso
7b
7c
7d
2.020
2.016
2.012
1.979
1.980
1.978
1.810
1.807
1.813
1.936
1.935
1.934
16.9
20.1
21.0
35.3
35.0
34.5
18.0
25.8
24.1
24.0
26.0
25.2
1.929
1.932
1.927
a Bg\=1/3(g1+g2+g3); BA\=1/3(A1+A2+A3); gi= 90.010, Ai= 92 G; experimental frequency w=9.44 GHz.
b T=100 K.
c Evaluated by comparison of the relevant room-temperature and frozen solution data.
d Room temperature.

80
P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
Table 4
EPR parameters for 7b–7d
‘Ion-spray’ mass spectrometry in acetonitrile confi-
rms the above assignment. The spectrum of 7c shows,
in addition to the signal at 509/511 (191Ir 59.49, 193Ir
100) corresponding to [Ir(Me)Cp*(NO)(PMe2Ph)]+, a
peak at m/z 520/522, corresponding to the substitution
product of NO by acetonitrile, and peaks at m/z 479/
Species
g1
g2
g3
A1 (G)
A2 (G)
A3 (G)
7b
7c
7d
2.009
2.014
1.949
1.975
1.978
1.916
1.819
1.814
1.762
18.40
15.82
16.77
34.50
33.70
33.64
16.41
25.65
25.32
products of 4b–4d are less easily reduced than 1b+
1d+.
–
Reduction of 4b–4d with [CoCp2] in CH2Cl2 has
been followed by EPR spectroscopy at temperatures
between 93 and 293 K, the signals of the products
becoming strong enough to be observed at 223 K. Such
signals disappear in a few days at room temperature,
because the one-electron reduction products 7b–7d are
further reduced to diamagnetic EPR silent species. This
occurs even by using lower than stoichiometric amounts
of cobaltocene (Co/Ir=0.5) which, being very soluble
in CH2Cl2, is still in excess over the almost insoluble
dication. 7b–7d give single line spectra in solution at ca.
193 K, and give well solved EPR spectra showing an
hyperfine structure in the glass state at 93 K (Fig. 6).
These spectra consist of three components with some
delocalization of the unpaired electron on the iridium
nucleus. Then these compounds can be described as low
spin iridium(II) complexes having rhombic symmetry.
The spectral parameters are obtained by simulation and
are reported in Table 4.
Complexes 7b–7d have been identified as the one-
electron reduction products of 4b–4d with negligeable
rearrangement of the ligands: actually the EPR parame-
ters are practically identical to those of the electrochem-
ically generated reduction products of 4a–4d, and
electrochemistry has proved the chemical reversibility
of the first reduction process. Finally EPR spectra of
the isolated 7c and 7d (vide infra) are also identical to
those reported in Fig. 6.
Reduction of dications 4b–4d to the corresponding
monocations 7b–7d on a preparative scale has been
carried out by slow addition of a benzene solution of
cobaltocene to a benzene suspension of the dication.
Complex 7b was too unstable to be isolated, while 7c
and 7d were isolated as light maroon solids, which are
unstable in the air and soluble in dichloromethane,
acetone and acetonitrile, and were identified on the
basis of the spectroscopic and analytical data (Scheme
6).
IR spectra of 7c and 7d in dichloromethane solution
show intense N–O stretching absorptions at 1825 and
1823 cm−1, respectively, suggesting a linear coordina-
tion for the nitrosyl ligand. These absorptions occur at
frequencies which are lower than those of the corre-
sponding dications 4c (1902 cm−1) and 4d (1903
cm−1), as expected because of stronger M“NO back-
bonding.
Fig. 6. EPR spectrum of 7c from the one-electron reduction of 3c
with [CoCp2] in CH2Cl2 at 93 K; (a) observed; (b) simulated.

P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
81
with CD3CN gave exclusively [Ir(Me)Cp*(CD3CN)-
(PMe3)]BF4.
As a further structural confirmation, oxidation of 7d
in CH2Cl2 with 1 equivalent of NOBF4 gives exclusively
4d (Scheme 7):
Further reduction of 7b–7d gives intractable reaction
mixtures, which have not been further investigated.
2.4. Reaction of [Ir(Me)2Cp*(NO)]BF4 (2) and
[Ir(Me)Cp*(NO)(L)](BF4)2 (L=PMePh2 4b, PMe2Ph
4c, PMe3 4d) with phosphines
Scheme 6.
We have reported in Section 2.2 that the nitrosyl
derivative 4d was found to undergo substitution of
NO+ by acetonitrile. We then looked if other reactants
such as phosphines could induce the NO+ displace-
ment reaction.
By treatment of 2 with PPh3 in CD2Cl2, the colour
changes from yellow to maroon and 1H-NMR monitor-
ing shows that 2 is disappeared and is partially (B10%)
converted to 1a. Since the solution remains clear and
no other signal is present, this means that most of the
product has been converted to paramagnetic species,
probably deriving from the NO loss (Scheme 8).
Reacting 4b with equimolar amounts of PMePh2 in
acetone makes the colour to change from deep maroon
to yellow. Evaporation of the solvent gave an oil which
is soluble in CH2Cl2, acetone and acetonitrile. The
1H-NMR spectrum in CD2Cl2 shows the almost quanti-
tative formation of [Ir(Me)Cp*(PMePh2)2]BF4 (3b),
which was also prepared independently by reaction of
[Ir(Me)(Cl)Cp*(PMePh2)] with AgBF4 in CH2Cl2 in the
presence of PMePh2 (Scheme 9).
Scheme 7.
Complexes 4c and 4d react analogously with equimo-
lar amounts of PMe2Ph and PMe3 in acetone to give
almost quantitatively [Ir(Me)Cp*(PMe2Ph)2]BF4 and
[Ir(Me)Cp*(PMe3)2]BF4, respectively, which were syn-
thesized also by reaction of the corresponding
chloromethyl derivative [Ir(Me)(Cl)Cp*(L)] (L=
PMe2Ph, PMe3) with AgBF4 in the presence of the
appropriate phosphine in CH2Cl2.
Then not only 4b–4c, which give substitution of
NO+ by acetonitrile, but also 2, which is inert towards
acetonitrile, react with phosphines to give cleavage of
the Ir–NO bond with loss of NO+.
Scheme 8.
481 and 463/465 corresponding to the loss of NO, and
NO and CH4, respectively.
In the mass spectrum of 7d the parent peak is absent,
but significant peaks are present which correspond to
the substitution of NO by acetonitrile (458/460), the
loss of NO (417/419), and of NO and CH4 (401/403).
As a confirmation of this interpretation reaction of 7
Scheme 9.

82
P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
Scheme 10.
3. Conclusions
dard techniques. The solvents were dried and distilled
prior to use. The compounds [Ir(Me)2Cp*(L)] (L=
PPh3 (1a) [15], PMePh2 (1b) [1c], PMe2Ph (1c) [1c],
PMe3 (1d) [1b]), [Ir(CD3)2Cp*(PMe3)] [1b], [Ir(Me)(Cl)-
Cp*(L)] (L=PPh3 [20], PMePh2 [20], PMe2Ph [1c],
PMe3 [21]) and [Rh(Me)2Cp*(PMe3)] [1b] were pre-
pared according to literature procedures. AgBF4 and
[FeCp2]PF6 were Aldrich products. NOBF4 (Aldrich
product) was treated under vacuum before use. 1H-,
31P-, 2H-NMR spectra were recorded on Varian Gemini
200 and VXR 300 instruments. EPR spectra for the
chemical oxidation and reduction reactions were ob-
tained by using EPR Varian E 112 instrument equipped
with a Varian E 257 for temperature control. The
spectrometer was interfaced to an AST Premium 486/25
by means of a data acquisition system consisting of an
acquisition board capable of acquiring up to 500 000
12-bit samples s−1, including 32-bit addition to mem-
ory, thus giving on-line signal averaging and a software
package specially designed for EPR experiments [22].
Materials and apparatus used for electrochemistry and
coupled EPR measurements have been described else-
where [23]. All the potentials values are referred to the
saturated calomel electrode (SCE): under the present
experimental conditions the one electron oxidation of
ferrocene occurs at +0.44 V in dichloromethane solu-
tion and at +0.46 V in acetone solution. Elemental
analyses were performed by the Laboratorio di Mi-
croanalisi of the Istituto di Chimica Organica, Facolta`
di Farmacia, University of Pisa.
We would like to make a few points on the chemistry
of the above cationic iridium nitrosyl derivatives. First
of all we would like to comment substitution reactions.
As we have described, some of the products of the
reaction with acetonitrile or phosphine derive formally
from the substitution of NO+ from the incoming lig-
and. Of course a possible explanation is that NO is
evolved leaving a paramagnetic complex which under-
goes a back reaction (Scheme 10), as it has been
suggested in the literature [18] for analogous reactions
of cationic ruthenium nitrosyl derivatives. In Scheme 10
is reported such a postulated mechanism for the reac-
tion of 2 with PPh3. Alternatively one could think of a
true displacement of NO+ from the dicationic complex.
More studies are clearly needed in order to fully explain
the observed behaviour.
Finally a comment on the EPR spectra of the one-
electron reduction products of 4b–4d, i.e. 7b–7d. As we
have already discussed, such nitrosyl complexes give
well solved patterns showing an hyperfine structure and
consisting of three components with some delocaliza-
tion of the unpaired electron on the iridium centre,
which can be then described as a low spin iridium(II)
system. Now, generally speaking, EPR studies reported
in the literature on nitrosyl complexes show invariably
the interaction of the unpaired electron with the NO
ligand. In such cases the coordination shell of the metal
retains its 18e structure, and the radical center is borne
by the ligand, and not by the metal. The iridium
complexes 7b–7d show instead a different delocaliza-
tion of the unpaired electron, as it results from the lack
of any hyperfine interaction with the nitrogen, and
from the observed coupling to the metal. As far as we
know, there are no other cases of a paramagnetic
transition metal system carrying a NO group and yet
showing no interaction with the nitrogen nucleus [19].
If one can define 19e complexes as having 19 VE with
a predominant metal character, this should be the case.
4.1. EPR spectral studies of the reaction of 1a–1d with
NOBF4
The reaction mixtures were prepared by placing a
weighed amount of metal complex (typically, 5 mg) and
NOBF4 (1–2 mg) into a quartz tube (o.d. 3 mm; i.d. 2
mm) fitted with a quartz–Pyrex joint and a Corning
Rotaflo Teflon tap (DISA, Milan). The tube was then
attached to a vacuum line and degassed by standard
vacuum/argon techniques; afterwards, it was immersed
in a dry ice-cooled acetone bath and then charged with
dichloromethane under pure argon atmosphere. The
quartz tube was then introduced into the spectrometer
cavity, pre-cooled to the desired temperature, and then
the reagents allowed to mix gradually. The hyperfine
4. Experimental
The reactions and manipulation of organometallics
were carried out under dinitrogen or argon, using stan-

P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
83
coupling constants and linewidths were obtained by
computer simulation of the EPR spectra.
4.4. Reaction of 1c with an excess of NOBF4 in
CH2Cl2: formation of [Ir(Me)Cp*(NO)(PMe2Ph)](BF4)2
(4c)
Complex 4c was prepared as above in 56% yield as a
maroon hygroscopic solid. Found: C, 32.87; H, 4.56; N,
1.18. C19H29B2F8IrNOP: Anal. Calc.: C, 33.28; H, 4.27;
N, 2.04%. IR (Nujol, cm−1) 1899 (s, NO), 1057 (BF4).
1H-NMR (CD3COCD3): l 2.28 (15 H, d, JHP=2.1 Hz,
C5Me5), 2.36 (3 H, d, JHP=5.3 Hz, IrMe), 2.56 (3H, d,
4.2. Reaction of 1a with NOBF4: formation of [Ir(Me)2
Cp*(NO)]BF4 (2) and [Ir(Me)Cp*(PPh3)2]BF4 (3a)
Complex 1a (0.05 g, 0.081 mmol) was dissolved in
CH2Cl2 (5 ml) and added with NOBF4 (0.010 g, 0.081
mmol). Methane (l 0.20, CD2Cl2) evolved and the
colour changed from light-yellow to golden-yellow. Af-
ter stirring for 3 h, the solvent was evaporated to
dryness; the residue was washed repeatedly with ben-
zene and dried under vacuum to give a mixture (0.029
g) of 2 (64%) and 3a (36%). By fractional crystallization
from acetone, pure 2 and 3a were obtained. Complex 2:
Found: C, 30.05; H, 4.40. C12H21BF4IrNO: Anal. Calc.:
C, 30.31; H, 4.45%. IR (Nujol, cm−1) 1843 (s, NO),
J
HP=12.5 Hz, PMe), 2.54 (3 H, d, JHP=11.9 Hz,
PMe). IS-MS (MeCN), m/e: 520 [M–NO+
+
MeCN]+, 479 [M–NO+]+, 463 [M–NO+ –MeH]+,
273 [M–MeNO+2MeCN]+ +
, , 87
254.7 [M]+ +
[BF4]−.
4.5. Reaction of 1d with an excess of NOBF4 in
CH2Cl2: formation of [Ir(Me)Cp*(NO)(PMe3)](BF4)2
(4d)
1
1054 (s, BF). H-NMR (CD3COCD3): l 1.81 (6 H, s,
1
IrMe), 2.25 (15 H, s, C5Me5). H-NMR (CD2Cl2): l
Complex 4d was prepared as above in 60% yield as a
deep orange solid. Found: C, 26.63; H, 4.50; N, 2.21.
C14H27B2F8IrNOP: Anal. Calc.: C, 26.96; H, 4.37; N,
2.25%. IR (Nujol, cm−1) 1903 (s, NO), 1056 (s, BF4).
1H-NMR (CD3COCD3): l 2.28 (9 H, d, JHP=12.6 Hz,
PMe), 2.31 (3 H, d, JHP=6.2 Hz, IrMe), 2.53 (15 H, d,
1.71 (6 H, s, IrMe), 2.14 (15 H, s, C5Me5). IS-MS
(MeOH), m/e: 386 [M]+, 370 [M–MeH]+, 340 [M–
MeH–NO]+, 326 [IrC5Me5]+, 87 [BF4]−. Complex 3a:
Found: C, 58.91; H, 4.91. C47H48BF4IrP2 Anal. Calc.:
C, 59.10; H, 5.07%. IR (Nujol, cm−1) 1062 (BF4).
1H-NMR (CD3COCD3): l 1.26 (15 H, t, JHP=2.2 Hz,
J
HP=1.9 Hz, C5Me5). 1H-NMR (CD3CN): l 1.97 (9 H,
1
C5Me5), 1.56 (3 H, t, JHP=4.9 Hz, IrMe). H-NMR
d, PMe), 2.05 (3 H, d, IrMe), 2.28 (15 H, d, C5Me5).
IS-MS (MeCN), m/e: 460 [M–NO+ +MeCN]+, 446
[M–H+]+, 417 [M–NO+]+, 401 [M–NO+ MeH]+,
224 [M]+ +, 87 [BF4]−.
(CD2Cl2): l 1.19 (15 H, t, C5Me5), 1.50 (3 H, t, IrMe);
IS-MS (MeOH), m/e: 866 [M]+, 603 [M–PPh3]+, 587
[M–PPh3–CH4]+. The same procedure as above was
used when 1a was reacted with an excess of NOBF4.
4.6. Reaction of 1d with equimolar amounts of NOBF4
in CD3CN: formation of [Ir(Me)Cp*(CD3CN)(PMe3)]
(BF4) (5d)
4.3. Reaction of 1b with an excess of NOBF4 in CH2
Cl2: formation of [Ir(Me)Cp*(NO)(PMePh2)](BF4)2
(4b)
Complex 1d (0.020 g, 0.046 mmol) was dissolved in
an NMR tube containing 1 ml of CD3CN, and NOBF4
(0.005 g, 0.046 mmol) was added causing an immediate
colour variation from light yellow to deep yellow, and
gas (CH4, l 0.19) formation. The mixture was stirred at
room temperature for 24 h, thereafter the 1H-NMR
spectrum showed the formation of 5d as the only
Complex 1b (0.1 g, 0.18 mmol) in CH2Cl2 (5 ml) was
reacted with NOBF4 (0.042 g, 0.36 mmol). The reaction
mixture was stirred at room temperature for 3 h.
Methane was evolved and a deep-orange solid was
formed, which was washed repeatedly with CH2Cl2 and
C6H6, and then dried under vacuum. Complex 4b was
obtained as a maroon hygroscopic solid (0.071 g, 53%).
Found: C, 36.98; H, 1.71; N, 3.83. C24H31B2F8IrNOP:
Anal. Calc.: C, 38.54; H, 1.87; N, 4.18%. IR (Nujol,
1
product. H-NMR (CD3CN): l 0.44 (3 H, d, JHP=6.6
Hz), 1.49 (9 H, d, JHP=10.7 Hz), 1.73 (15 H, d,
J
HP=2.1 Hz).
4.7. Reaction of [Ir(Me)(Cl)Cp*(PMe3)] with AgBF4 in
CD3CN: formation of [Ir(Me)Cp*(CD3CN)(PMe3)]
(BF4)2 (6d)
cm−1
)
1900 (s, NO), 1059 (BF4). 1H-NMR
(CD3COCD3): l 2.25 (3 H, d, JHP=4.8 Hz, IrMe), 2.30
(15 H, d, JHP=1.9 Hz, C5Me5), 2.96 (3H, d, JHP=11.6
Hz, PMe), 7.7–8.2 (10 H, bm, Ph). 1H-NMR (CD3CN):
l 2.02 (3 H, d, IrMe), 2.09 (15 H, d, C5Me5), 2.55 (3H,
d, PMe), 7.3–7.65 (10 H, bm, Ph). IS-MS, m/e: 585
[M–NO+ +MeCN]+, 543 [M–NO+]+, 527 [M–
NO+ MeH]+, 286 [M]+ +, 263 [M–MeNO]+ +, 87
[BF4]−.
1
AgBF4 (0.011 g, 0.055 mmol) was added to a H-
NMR tube containing [Ir(Me)(Cl)Cp*(PMe3)] (0.025 g,
0.055 mmol) dissolved in CD3CN (1 ml). AgCl formed
immediately. After 2 h the suspension was filtered and
1
the clear solution examined by H-NMR was found to
contain 5d as the only product.

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P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
4.8. Reaction of 1d with an excess of NOBF4 in CD3-
CN: formation of [Ir(Me)Cp*(NO)(PMe3)](BF4)2 (4d),
[Ir(Me)Cp*(CD3CN)(PMe3)](BF4) (5d) and [IrCp*
(CD3CN)2(PMe3)](BF4)2 (6d)
stirred suspension of [Ir(Me)Cp*(NO)(PMe2Ph)](BF4)2
(4c) (0.038 g, 0.055 mmol), in benzene (1 ml). After the
addition was over (ca. 1 h) the reaction mixture was
stirred for 2 h at room temperature. A solid formed,
which was separated from the solution, washed with
benzene and dried under vacuum. The solid was ex-
tracted with CH2Cl2 (5 ml), and the clear solution
resulting from the filtration, was dried under vacuum to
give a light-maroon residue which was identified as
[Ir(Me)Cp*(NO)(PMe2Ph)]BF4 (7c) (yield 35%). Found:
C, 36.89; H, 4.50; N, 1.85. C19H29BF4IrNOP: Anal.
Calc.: C, 38.12; H, 4.89; N, 2.34%. FT-IR (CH2Cl2):
1825 (s, NO); 1078 (s, BF) cm−1. IS-MS (CH3CN): m/e
520 [M–NO+MeCN]+; 509 [M]+; 479 [M–NO]+;
463 [M–NO–CH4]+.
Complex 1d (0.018 g, 0.041 mmol) was dissolved in
an NMR tube containing 1 ml of CD3CN, and NOBF4
(0.010 g, 0.086 mmol) was added causing an immediate
colour variation from light yellow to deep yellow, and
1
gas (CH4, l 0.19) formation. The H-NMR spectrum
shows the presence of 4d, 5d and 6d in roughly equiva-
lent amounts. After 1 week at room temperature, only
1
5d and 6d are present in equimolar ratio (by H-NMR).
Complex 6d: 1H-NMR (CD3CN): l 1.74 (9 H, d,
J
HP=11.8 Hz), 1.79 (15 H, d, JHP=2.3 Hz).
4.9. Reaction of [IrCl2Cp*(PMe3)] with AgBF4 in
CD3CN: formation of [IrCp*(CD3CN)2(PMe3)](BF4)2
(6d)
4.13. Reaction of [Ir(Me)Cp*(NO)(PMe3)](BF4)2 (4d)
with [CoCp2]: formation of [Ir(Me)Cp*(NO)(PMe3)]
(BF4) (7d)
1
AgBF4 (0.016 g, 0.084 mmol) was added to a H-
A total of 9 ml of a benzene solution of cobaltocene
(0.024 M, 0.22 mmol) were added dropwise under
stirring to a suspension of [IrMe(NO)Cp*(PMe3)](BF4)2
(4d) (0.032 g, 0.052 mmol) in benzene (1 ml). After the
addition was over (ca. 1 h), the reaction mixture was
stirred for further 2 h. A solid was separated from the
solution, washed repeatedly with benzene and dried
under vacuum. The resulting dark maroon solid was
treated with 5 ml of CH2Cl2, and after filtration the
clear solution was dried under vacuum to give [Ir-
Me(NO)Cp*(PMe3)]BF4 (7d) as a light maroon solid
(45%). Found: C, 30.85; H, 4.64; N, 2.21.
C14H27BF4IrNOP: Anal. Calc.: C, 31.33; H, 5.08; N,
2.61%. FT-IR (CH2Cl2): 1823 (s, NO); 1071 (s, BF)
cm−1. IS-MS (CH3CN): m/e 458 [M–NO+MeCN]+;
417 [M–NO]+; 401 [M–NO–CH4]+.
NMR tube containing [IrCl2Cp* (PMe3)] (0.02 g, 0.042
mmol) dissolved in CD3CN (1 ml). AgCl formed imme-
diately. After 2 h the suspension was filtered and the
clear solution examined by 1H-NMR was found to
contain 6d as the only product.
4.10. Reaction of [Ir(Me)Cp*(NO)(PMePh2)](BF4)2
(4b) with CD3CN: formation of [IrCp*(CD3CN)2(PMe
Ph2)](BF4)2 (6b)
A sample of [Ir(Me)Cp*(NO)(PMePh2)](BF4)2 (4b)
(0.030 g, 0.040 mmol) was dissolved in an NMR tube
containing 1 ml of CD3CN. The H-NMR spectrum
shows the formation of a new compound in addition to
the starting product. After 4 days 4b was quantitatively
converted into [IrCp*(CD3CN)2(PMePh2)](BF4)2 (6b),
identified by comparison of the 1H-NMR spectrum
1
4.14. Reaction of [Ir(Me)Cp*(NO)(PMe3)]BF4 (7d)
with CD3CN: formation of [Ir(Me)Cp*(CD3CN)-
(PMe3)]BF4 (5d)
1
with that of a sample obtained by synthesis. H-NMR
(CD3CN): l 1.61 (15 H, d, JHP=2.2 Hz, C5Me5), 2.45
(3 H, d, JHP=10.7 Hz, PMe). 31P-NMR (CD3CN): l
−3.62.
[Ir(Me)Cp*(NO)(PMe3)]BF4 (7d) (0.030 g, 0.056
mmol) was dissolved in a NMR tube containing 1 ml of
CD3CN. The 1H-NMR spectrum showed exclusively
the signals of a product which has been identified as
[Ir(Me)Cp*(CD3CN)(PMe3)]BF4 (5d) by comparison
4.11. EPR spectral studies of the reaction of 4b–4d
with [CoCp2]
1
By using the same procedure described in 4.1, 4b–4d
(typically ca. 5 mg) were reacted with CoCp2 (ca. 2 mg)
in CH2Cl2.
with the H-NMR of an authentic sample.
4.15. Reaction of [Ir(Me)Cp*(NO)(PMe3)]BF4 (7d)
with NOBF4: formation of [Ir(Me)Cp*(NO)(PMe3)]-
(BF4)2 (4d)
4.12. Reaction of [Ir(Me)Cp*(NO)(PMe2Ph)](BF4)2 (4c)
with [CoCp2]: formation of [Ir(Me)Cp*(NO)(PMe2Ph)]-
BF4 (7c)
NOBF4 (0.023 g, 0.020 mmol) was added to a
CH2Cl2 solution (3 ml) of [Ir(Me)Cp*(NO)(PMe3)]BF4
(7d) (0.011 g, 0.020 mmol). Soon after the mixing of the
reactants, a solid deep-maroon formed which, after 1 h
A total of 9.5 ml of a benzene solution of cobal-
tocene (0.024 M, 0.23 mmol) were added dropwise to a

P. Di6ersi et al. / Journal of Organometallic Chemistry 584 (1999) 73–86
85
of stirring, was separated from the solution, washed
repeatedly with CH2Cl2 and dried. The solid resulted to
be [IrMeCp*(NO)(PMe3)](BF4)2 (4d) (60%) identified
by comparison with an authentic sample.
with pentane, and dried under vacuum to give 0.024 g
(81%) of [Ir(Me)Cp*(PPh3)2]BF4 (3a).
The complexes 3b–3c have been prepared in a similar
way from [Ir(Me)(Cl)Cp*(PMePh2)] and [Ir(Me)(Cl)-
Cp*(PMe2Ph)] by reaction with PMePh2 and PMe2Ph,
respectively.
4.16. Reaction of [Ir(Me)2Cp*(NO)]BF4 (2) with PPh3
Complex 3a: 1H-NMR (CD2Cl2): l 1.19 (15 H, t,
J
HP=2.2 Hz, C5Me5); 1.50 (3H, t, JHP=4.9 Hz, IrMe).
A solution of PPh3 (0.005 g, 0.020 mmol) in 0.7 ml of
CD2Cl2 was added to [Ir(Me)2Cp*(NO)]BF4 (0.020
mmol) (2). The colour of the solution changed immedi-
1H-NMR (CD3COCD3): l 1.26 (15H, t, C5Me5), 1.56
(3H, t, IrMe). IS-MS (CH3OH): m/e 866 [M]+; 603
[M–PPh3]+; 587 [M–PPh3–CH4]+.
1
ately from yellow to maroon. The H-NMR spectrum
Complex 3b: Found: C, 54.20; H, 5.31.
showed only the presence of [Ir(Me)2Cp*(PPh3)] (1a).
1H-NMR (CD2Cl2): l −0.05 (6 H, d, JHP=5.0 Hz,
IrMe), 1.39 (15 H, d, JHP=1.8 Hz, C5Me5), 7.15−7.55
(15 H, m, PPh3).
1
C37H44BF4IrP2: Anal. Calc.: C, 53.48; H, 5.34%. H-
NMR (CD2Cl2): l 1.01 (3 H, t, JHP=5.4 Hz, IrMe),
1.35 (3 H, d, JHP=10.0 Hz, PMe), 1.40 (15 H, t,
J
HP=2.2 Hz, C5Me5), 7.20–7.60 (10 H, bm, Ph).
Complex 3c: Found: C, 45.33; H, 6.12.
4.17. Reaction of [Ir(Me)Cp*(NO)(PMePh2)](BF4)2
(4b) with PMePh2: formation of [Ir(Me)Cp*(PMe-
Ph2)2]BF4 (3b)
1
C27H40BF4IrP2: Anal. Calc.: C, 45.88; H, 5.71%. H-
NMR (CD2Cl2): l 0.54 (3 H, t, JHP=6.0 Hz, IrMe),
1.50 (6 H, d, JHP=10.0 Hz), 1.58 (15 H, t, JHP=2.0
Hz, C5Me5), 7.2–7.60 (5 H, bm, Ph).
PMe2Ph (0.011 ml, 0.080 mmol) was added to
[Ir(Me)Cp*(NO)(PMe2Ph)](BF4)2 (4b) (0.020 g, 0.027
mmol) in acetone (3 ml). The reaction mixture was
stirred for 1 h, then evaporation of the solvent under
reduced pressure gave a maroon oil, identified as
[Ir(Me)Cp*(PMePh2)2]BF4 (3b) (98% yield) by compari-
1
Complex 3d: H-NMR (CD3COCD3): l 1.88 (15 H,
t, JHP=1.9 Hz, C5Me5), 1.66 (18 H, vt, JHP=10.4 Hz,
PMe3), 0.24 (3H, t, JHP=6.3 Hz, IrMe).
Acknowledgements
1
son of the H-NMR spectrum with that of a sample
prepared as described in Section 4.19.
We thank CNR (Rome) for financial support. P.Z.
acknowledges the technical assistance of G. Monto-
moli. P.D. acknowledges the assistance of F. Simoncini
and V. Ermini.
4.18. Reaction of [Ir(Me)Cp*(NO)(PMe2Ph)](BF4)2 (4c)
with PMe2Ph: formation of [Ir(Me)Cp*(PMe2Ph)2]BF4
(3c)
A solution of PMe2Ph (0.0125 ml, 0.0875 mmol) in
acetone (3 ml) was added to [Ir(Me)Cp*(NO)(PMe2-
Ph)](BF4)2 (4c) (0.020 g, 0.029 mmol). The colour
changed from deep-maroon to pale-yellow. The mixture
was stirred for 1 hr. By evaporation at reduced pres-
sure, an oil was obtained and washed repeatedly with
ether to give [Ir(Me)Cp*(PMe2Ph)2]BF4 (3c) as a light-
maroon solid, identified by comparison with a sample
obtained as described in Section 4.19.
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