Catalytic and stoichiometric reactions of tertiary silanes with [Ir(Me)2Cp*L] (Cp=η5-C5Me5; L=PMe3, PMe2Ph, PMePh2, PPh3) in the presence of one-electron oxidants. A unique case of Si-H, Si-C, Ir-C and P-F bonds one-step activation: Crystal structure of [Ir(Ph)(SiPh2F)Cp*(PMe3)]

Article abstract of DOI:10.1016/S0022-328X(99)00469-6

The iridium(III) dimethyl derivatives [Ir(Me)₂Cp*L] (Cp=η⁵-C₅Me₅; L=PMe₃ 1a, PPh₃ 1d) catalyze the dehydrogenative coupling of dimethylphenylsilane in the presence of one-electron oxidants to yield Me₂PhSiSiPhMe₂. Compounds 1a-d react with triphenylsilane in the presence of [FeCp₂]PF₆ to give methane and [Ir(Ph)(SiFPh₂)Cp*L] (L=PMe₃ (2a), PMe₂Ph (2b), PMePh₂ (2c), PPh₃ (2d)). 2a was structurally characterized by single-crystal X-ray diffraction experiments. The `three-legged piano stool' coordination polyhedron is slightly deformed.

Full text of DOI:10.1016/S0022-328X(99)00469-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 593–594 (2000) 154–160
Catalytic and stoichiometric reactions of tertiary silanes with
[Ir(Me)2Cp*L] (Cp*=h5-C5Me5; L=PMe3, PMe2Ph, PMePh2,
PPh3) in the presence of one-electron oxidants. A unique case of
SiꢀH, SiꢀC, IrꢀC and PꢀF bonds one-step activation: crystal
structure of [Ir(Ph)(SiPh2F)Cp*(PMe3)]
Pietro Diversi a,*, Fabio Marchetti b, Valentina Ermini a, Simona Matteoni a
a Dipartimento di Chimica e Chimica Industriale dell’Uni6ersita` di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
b Dipartimento di Ingegneria Chimica dei Materiali e delle Materie Prime e Metallurgia dell’Uni6ersita` ‘La Sapienza’,
Via del Castro Laurenziano 7, I-00195 Rome, Italy
Received 28 May 1999; accepted 2 August 1999
Abstract
The iridium(III) dimethyl derivatives [Ir(Me)2Cp*L] (Cp*=h5-C5Me5; L=PMe3 1a, PPh3 1d) catalyze the dehydrogenative
coupling of dimethylphenylsilane in the presence of one-electron oxidants to yield Me2PhSiSiPhMe2. Compounds 1a–d react with
triphenylsilane in the presence of [FeCp2]PF6 to give methane and [Ir(Ph)(SiFPh2)Cp*L] (L=PMe3 (2a), PMe2Ph (2b), PMePh2
(2c), PPh3 (2d)). 2a was structurally characterized by single-crystal X-ray diffraction experiments. The ‘three-legged piano stool’
coordination polyhedron is slightly deformed. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Iridium; Electron-transfer catalysis; Silanes; Dehydrocoupling
1. Introduction
plexes resulting from a novel one-step rearrangement of
SiꢀH, SiꢀC, IrꢀC, and PꢀF bonds.
We have described in previous papers [1] the reac-
tions of the Ir(III) dimethyl complexes [Ir(Me)2Cp*L]
(L=PMe3 (1a), PMe2Ph (1b), PMePh2 (1c), PPh3 (1d))
with arenes under oxidative conditions to give methane
and the corresponding methylaryl derivatives
[Ir(Me)(Ar)Cp*L] via a ‘s-bond metathesis’ reaction of
IrꢀC and CꢀH bonds. With the aim to extend the
applicability of this reaction we have moved our atten-
tion to the activation of SiꢀH bonds, which are known
to undergo a variety of catalytic [2] and stoichiometric
[3] reactions in the presence of transition metals. Here
we report that the above iridium derivatives in the
presence of one-electron oxidants are able to catalyze
the deydrogenative coupling of PhMe2SiH to the disi-
lane and react with Ph3SiH to give new iridium com-
2. Results and discussion
The reaction of PhMe2SiH in the presence of cata-
lytic amounts of 1a or 1d and one-electron oxidants
([FeCp2]PF6, AgBF4) in CH2Cl2 showed formation of
the product of dehydrogenative coupling PhMe2-
SiSiMe2Ph (Table 1):
2PhMe2SiH“PhMe2SiSiMe2Ph+H2
Compound 1a proved to be a better catalyst precursor
than 1d. The yields depend significantly on the temper-
ature and on silane/catalyst ratio, being quite low (2%)
at room temperature (r.t.) and at a silane/iridium ratio
of 1000, but increasing remarkably (up to 71%) with the
temperature (80°C) and by decreasing the silane:iridium
ratio (400). No detectable amounts of disilane form in
the absence of the oxidant agent.
* Corresponding author. Fax: +39-050-918-260.
E-mail address: div@dcci.unipi.it (P. Diversi)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00469-6

P. Di6ersi et al. / Journal of Organometallic Chemistry 593–594 (2000) 154–160
155
Table 1
Dehydrocoupling of PhMe2SiH in the presence of [Ir(Me)2Cp*L]/oxidant
a
Complex
Ox
Ox/Ir b
Si/Ir b
T (°C)
Time (days)
(PhMe2Si)2 yield (%)
Ph2MeSiH yield (%)
1a
1a
1a
1a
1d
1d
1a
1a
[FeCp2]+
[FeCp2]+
[FeCp2]+
[FeCp2]+
[FeCp2]+
[FeCp2]+
Ag+
2.0
2.0
2.5
2.5
2.0
2.0
2.5
2.5
1000
1000
400
25
40
80
80
25
40
80
80
6
6
1
2
6
6
2
2
2.5
8
37
–
–
3.4
–
–
–
400
71
1000
1000
400
0.6
2.2
5 c
25
–
17.5
Ag+
400
a Ox, oxidant; reactions carried out using 6.3 mmol of silane in 1.6 ml of CH2Cl2.
b Molar ratio.
c In a sealed tube.
The yields are lower in the presence of AgBF4 or in
a sealed system, as it is to be expected for a reaction
which proceeds with formation of dihydrogen.
It has to be noted that, depending on the experimen-
tal conditions, formation of Ph2MeSiH was also ob-
served. This product does not form at all if the reaction
is carried out in a closed system. It is possible that
Ph2MeSiH formed by disproportionation of the starting
silane.
Other silanes such as Ph2MeSiH and Ph3SiH do not
give dehydrocoupling products under the above condi-
tions probably because of the greater steric require-
ments due to the presence of the aromatic groups
(although in the case of Ph3SiH small amounts of
Ph3SiOSiPh3 have been occasionally observed, as it is
reported to occur for dehydrocoupling reactions cata-
lyzed by late transition metal systems [2a,b] in the
presence of adventitious traces of water or dioxygen).
Instead Ph3SiH reacts stoichiometrically with 1a–d to
give new organometallic complexes which have been
isolated and characterized. When a slight excess of
triphenylsilane and a 1:1 ferrocenium:iridium ratio are
used, formation of the new organometallic complexes 2
takes place, which contain an IrꢀPh and an IrꢀSiFPh2
bond (Scheme 1).
2PhMe2SiH“Ph2MeSiH+Me3SiH
Transition-metal catalyzed redistribution reactions,
which exchange groups bonded to silicon are well
known [2c,4].
In general the catalytic systems reported in the litera-
ture are inactive or poorly active for the dehydrogena-
tive coupling of tertiary silanes, the order of reactivity
being tertiaryBsecondaryBprimary [2]. Then the ac-
tivity of our system towards PhMe2SiH is an interesting
peculiarity since only a few catalysts are able to cata-
lyze the dehydrogenative coupling of monohydrosilanes
(PhMe2SiH, Ph2MeSiH) [5]. The best yields (71%) of
(PhMe2Si)2 we have obtained are remarkably high, if
compared with those reported in the literature for
tertiary silanes: for instance, dehydrogenative coupling
of PhMe2SiH proceeds only with 7% yield in the pres-
ence of [Pt(PMe2Ph)4] at 150°C [5b].
In the literature two main reaction pathways have
been proposed for dehydrocoupling reactions, a con-
certed mechanism for the early transition-metal cata-
lyzed reactions, and an oxidative addition/reductive
elimination sequence for the late transition-metal cata-
lyzed reactions [5]. However we are inclined to prefer
the first one in analogy to what we have proposed for
some arene CꢀH activation reactions observed with the
same iridium/oxidant system [1]. As for the role of the
one-electron oxidant we believe that its presence is
necessary in order to trigger the reductive elimination
steps of methane which lead eventually to the active
species [Ir(SiMe2Ph)Cp*(L)]+.
The reaction proceeds rapidly at r.t. by adding
equimolar amounts of [FeCp2]PF6 to a solution of
1a–d in dichloromethane containing an excess of
triphenylsilane. A gas evolves from the surface of the
1
oxidant which by monitoring the reaction by H-NMR
spectroscopy in CD2Cl2 was identified as methane (l
0.20 ppm, s). After ca. 1 h at r.t., it was found that
1a–d have been almost quantitatively converted into
the new organometallic compounds 2a–d. These prod-
ucts were isolated from the reaction mixture as pale–
yellow crystals, soluble in dichloromethane, benzene
1
and relatively stable in the air. The H-NMR spectrum
Scheme 1.

156
P. Di6ersi et al. / Journal of Organometallic Chemistry 593–594 (2000) 154–160
(h5 - pentamethylcyclopentadienyl) ꢀ phosphino ꢀ silyl
derivatives of Ir(III) [3,8]. The IrꢀC(11) distance may
instead be compared with those found in other
5
,
Ir(III)ꢀphenyl derivatives: by instance 2.076 A in (h -
pentamethylcyclopentadienyl)ꢀtrimethylphosphinoꢀtri-
,
A
fluoromethanesulfonylꢀphenylꢀiridium [9], 2.063
in (h5 - ethyl(tetramethyl) ꢀ cyclopentadienyl) ꢀ fluoroꢀ
,
phenylꢀtrimethylphosphineꢀiridium [6] or 2.094 A in
(Z) - (h5 - pentamethylcyclopentadienyl)ꢀtrimethylphos-
phinoꢀ(1 - hydroxy - 1,2 - bis(methoxycarbonyl)ethenyl)ꢀ
phenylꢀiridium [9]. Provided that the ‘three-legged pi-
ano stool’ may be considered as an octahedral coordi-
nation where three corners are occupied by the Cp*, the
bond angles among the ‘legs’ of the ‘stool’ are normally
found closely near to 90°. This value is observed also in
this case, with minor deviations (B3°) due to the
different hindrance of the ligands, the greatest angles
being those adjacent to the iridium phosphorus bond.
Fig. 1. Molecular structure of [Ir(Ph)(SiFPh2)Cp*(PMe3)] (2a).
is characterized by the presence of signals due to the
pentamethylcyclopentadienyl ligand, the phosphine,
and a series of aromatic multiplets. For instance the
spectrum of 2a in CD2Cl2 shows two doublet reso-
nances at 1.32 ppm (JHP=1.79 Hz) and 1.57 ppm
(JHP=9.9 Hz) assigned to the C5Me5 and PMe3 proton
atoms, and a multiplet between 6.9 and 7.7 ppm due to
the aromatic protons. The 31P-NMR spectrum in C6D6
shows a singlet at −45.5 ppm, which is consistent with
the observed values of related half-sandwich
trimethylphosphino complexes of Ir(III) [1b,6]. More-
over the 19F-NMR resonances of 2a–d present the 29Si
(nuclear spin 1/2, 4.7% abundance) satellites which
indicate that the Si and F atoms are connected. The
chemical shifts of the fluorine nuclei are in agreement
with those reported in the literature for systems con-
taining SiꢀF bonds [6,7].
In order to clarify the nature of these products,
crystals of 2a suitable for an X-ray analysis were pre-
pared by slow crystallization from dichloromethane/
pentane solutions. The X-ray structure determination
has established that in addition to the Cp* and phos-
phine ligands the iridium center is bonded to a phenyl
and a SiFPh2 group. The molecular structure of 2a is
shown in Fig. 1. The coordination around the metal is
the usual ‘three-legged piano stool’ generally found in
half-sandwich derivatives of Ir(III). The bonding ge-
ometry around the metal is listed in Table 2. The
coordination distances are in keeping, within the stan-
dard deviations, with the values generally found in
It is interesting to observe that Ph3SiH does also
¸¹¹¹º
react with [Ir(C6H4PPh2)(Me)Cp*] [1a,b] in the presence
of [FeCp2]PF6 to give 2d, with similar rates and reac-
tion times. Analogously 2c is also obtained by reaction
¸¹¹¹º
of Ph3SiH with [Ir(C6H4PMePh)(Me)Cp*] [1c].
Under the above stoichiometric conditions
PhSiMe2H gave poor yields of complex mixtures of
organometallic compounds which we have not been
able to characterize.
The formation of 2a–d is a complex reaction by
which two IrꢀC bonds, the SiꢀH and SiꢀC bonds of
triphenylsilane and a PꢀF bond of the PF−6 anion are
cleaved, and IrꢀSi, IrꢀC and SiꢀF bonds are formed,
with concurrent elimination of 2 mol of methane per
mole of complex. A plausible mechanism is shown in
the Scheme 2.
The role of the oxidant, besides being the source of
fluorine which is bonded to the silicon atom in the final
product, is that of triggering the homolysis reaction of
the IrꢀMe bond which is a prerequisite for the activa-
tion of silane. Since methane does not incorporate
deuterium in the reaction carried out in CD2Cl2, at least
half of the methane produced is eliminated intramolec-
ularly. Although at the moment we have no other
evidence, we think that a ‘tucked-in’ intermediate [10] is
operating in both the methane elimination steps. The
intermediacy of such species has been already demon-
strated for CꢀH activation reactions under oxidative
conditions [1c] with the same iridium systems, but other
routes are of course possible [11].
Then metathesis of IrꢀMe and SiꢀH bonds produces
a SiPh3 ligand, which undergoes SiꢀPh cleavage with
the phenyl group migrating to the iridium center and a
fluoride ion moving from the hexafluorophosphate an-
ion to the silicon atom. The route from the orthometal-
lated derivatives after the addition of the silane is
identical.
Table 2
a,b
,
Selected bond distances (A) and angles (°) around the metal in 2a
IrꢀC(11)
IrꢀP
SiꢀF
2.08(2)
2.266(6)
1.653(14)
IrꢀCp%
IrꢀSi
1.979(13)
2.318(7)
Cp%ꢀIrꢀC(11)
C(11)ꢀIrꢀP
Cp%ꢀIrꢀP
119.8(7)
91.1(6)
128.6(4)
Cp%ꢀIrꢀSi
PꢀIrꢀSi
C(11)ꢀIrꢀSi
124.0(4)
92.8(3)
90.4(6)
a Estimated standard deviations are given in parentheses.
b Cp% denotes the centroid of the Cp* ligand.

P. Di6ersi et al. / Journal of Organometallic Chemistry 593–594 (2000) 154–160
157
Scheme 2.
An interesting mechanistic question concerns the
transfer of a phenyl group from silicon to the iridium
atom. Transfer of an aryl group from silicon to a
transition metal to form a metalꢀaryl bond has been
case is produced by the reductive elimination of
methane promoted by the one electron oxidation of
the dimethyl compound 1.
Finally, a crucial point is the mechanistic signifi-
cance of these results in connection with the catalytic
reactions. Our opinion is that the same intermediate
which has been proposed in the Scheme 2,
[Ir(SiR3)Cp*(L)]+, is the active species for the dehy-
drocoupling and that only a delicate balance of steric
and electronic properties of the silane, according to
the nature of the groups attached to silicon, may de-
cide which is the preferred reaction pattern. Work is
in progress in order to verify these ideas.
previously observed [6,12]. The occurrence of
a
cationic silylene intermediate (possibly generated via
1,2-shifts between the metal and silicon) may be in-
volved (Scheme 2). A related cationic silylene ruthe-
nium complex has been recently isolated [13].
Alternatively the cationic silyl intermediate may un-
dergo F− attack and migration of the phenyl group to
the iridium center.
These mechanistic pathways have been already pro-
posed for other rearrangement reactions of substituted
silyl groups bonded to an iridium center [6,12b]. In
particular the same cationic methyl intermediate
[Ir(Me)Cp*(PMe3)]+, which is reported to derive from
ionization of the starting trifluoromethanesulfonato
complex [Ir(Me)(OSO2CF3)Cp*(PMe3)] [12b], in our
3. Experimental
The reactions and manipulation of organometallics
were carried out under dinitrogen or argon, using

158
P. Di6ersi et al. / Journal of Organometallic Chemistry 593–594 (2000) 154–160
standard techniques. The solvents were dried and dis-
tilled prior to use. The compounds [Ir(Me)2Cp*(L)]
(L=PMe3 (1a) [1b], PMe2Ph (1b) [1c], PMePh2 (1c)
[1c], PPh3 (1d) [1b]), were prepared according to litera-
ture procedures. Commercial reagents, AgBF4,
[FeCp2]PF6, Ph3SiH, PhMe2SiH and Ph2MeSiH were
3.2.1. Complex 2a
Anal. Found: C, 55.2; H, 5.7. C31H39FIrPSi Calc.: C,
54.6; H, 5.8%; 1H-NMR (CD2Cl2): l 1.32 (9H, d,
JHP=9.9 Hz, PMe3), 1.57 (15H, d, JHP=1.8 Hz,
C5Me5), 6.9–7.7 (15H, bm, Ph); (C6D6): l 1.11 (9H, d,
PMe3), 1.47 (15H, d, C5Me5), 6.7–7.4 (bm, Ph). 13C-
NMR (C6D6): 9.81 (s, C5Me5), 18.41 (d, JCP=38 Hz,
PMe3), 97.32 (s, C5Me5), 122.5, 127.4, 127.5, 127.6,
127.7, 128.6, 135.1, 135.3, 144.6 (d, JCP=3.7 Hz) (Ph).
19F-NMR (C6D6): l −151.12 (d, JSiF=316 Hz).
used as supplied. H, 13C, 31P, 19F, H-NMR spectra
were recorded on Varian Gemini 200 and VXR 300
instruments. Elemental analyses were performed by
the Laboratorio di Microanalisi of the Istituto di
Chimica Organica, Facolta` di Farmacia, University of
Pisa.
1
2
3.2.2. Complex 2b
Anal. Found: C, 57.8; H, 5.4. C31H39FIrPSi Calc.: C,
58.1; H, 5.5%; 1H-NMR (CD2Cl2): l 1.23 (3H, d,
3.1. Reaction of dimethylphenylsilane in the presence of
1a or 1b and [FeCp2]PF6 or AgBF4: general procedure
JHP=10.1 Hz, PMe), 1.42 (3H, d, JHP=9.7 Hz, PMe),
1.48 (15H, d, JHP=1.9 Hz, C5Me5), 6.8–7.7 (bm, Ph);
(C6D6): l 1.17 (3H, d, PMe), 1.26 (3H, d, PMe), 1.40
(15H, d, C5Me5), 7.0–8.0 (bm, Ph). 19F-NMR (C6D6): l
−148.9 (d, JSiF=312 Hz).
The reaction of Ph2MeSiH in the presence of 1a and
[FeCp2]PF6 is reported as an example. Ph2MeSiH (1 ml,
6.3 mmol), 1a (6.8 mg, 0.016 mmol) and [FeCp2]PF6
(13.0 mg, 0.039 mmol) were introduced under argon
atmosphere in a two-necked flask equipped with a
reflux condenser and a stirbar, and 1.6 ml of anhydrous
deoxygenated CH2Cl2 were added. The reaction mix-
ture was heated for the desired time at constant temper-
ature, then, after removal of the volatiles, the residue
was eluted through a column of alumina by using a
benzene/pentane mixture. The oily residue was exam-
ined by 1H-NMR spectroscopy. (Me2PhSi)2 [14] and
Ph2MeSiH were identified on the basis of spectroscopic
data.
3.2.3. Complex 2c
Anal. Found: C, 60.9; H, 5.5. C41H43FIrPSi Calc.: C,
61.1; H, 5.4%. 1H-NMR (CD2Cl2): l 1.05 (3H, d,
J
HP=10.1 Hz, PMe), 1.46 (15H, d, JHP=1.7 Hz,
C5Me5), 6.8–7.7 (bm, Ph). 19F-NMR (C6D6): l −145.7
(d, JSiF=308.5 Hz).
3.2.4. Complex 2d
Anal. Found: C, 64.0; H, 5.3. C46H45FIrPSi Calc.: C,
63.6; H, 5.2%. 1H-NMR (CD2Cl2): l 1.45 (15H, d,
J
HP=2.0 Hz, C5Me5), 6.8–7.0 (bm, Ph). 19F-NMR
(Me2PhSi)2: 1H-NMR (CDCl3): l=0.32 (12H, s,
SiMe); 7.25–7.60 (10H, m, Ph) (Ref. [14] l=0.32).
(C6D6): l=0.31 (12H, s, SiMe); 7.20 (12H, m, Ph), 7.55
(8H, m, Ph). MS: m/z 270 (M+), 135.
(C6D6): l −142.3 (d, JSiF=305.4 Hz). 13C-NMR
(C6D6): 9.75 (s, C5Me5), 100.00 (s, C5Me5), 121.01–
145.39 (m, Ph).
1
Ph2MeSiH: H-NMR (CDCl3): l=0.63 (3H, d, J=
3.3. Crystallographic studies
3.7 Hz, SiMe); 4.95 (1H, q, J=3.9 Hz, SiH); 7.25–7.60
(10H, m, Ph). (CD2Cl2): 0.68 (3H, d, SiMe); 4.97 (1H,
q, SiH); 7.35–7.70 (10H, m, Ph).
Single crystals of 2a are colorless prisms. One of
them was mounted in nitrogen atmosphere on a
Siemens P4 diffractometer. Details about the crystal
parameters and intensity data collection are summa-
rized in Table 3. The diffraction symmetry and system-
atic absences suggested the Cc or C2/c as possible space
groups. The first was chosen on the basis of the cell
volume and the possible symmetry elements of the
molecule. The collected data were corrected for
Lorentz, polarization and absorption effects by means
of a C-scan method [15]. The structure solution was
obtained by means of direct methods by using the
TREF procedure contained in SHELXTL package [16].
Some degree of disorder in molecule conformation is
revealed by abnormally high values of some thermal
factors and by the inconsistent geometry of some rings.
The refinement was performed by constraining the
phenyl ring C(11)\C(16) and the pentamethylcy-
clopentadienyl ring C(1)\C(5) to have an ideal geome-
3.2. General procedure for the reaction of
[Ir(Me)2Cp*L] (1a–d) with SiPh3H and [FeCp2]PF6:
formation of [Ir(Ph)(SiPh2F)Cp*L] (2a–d)
Complexes 1a–d (20–30 mg), ferrocenium hex-
afluorophosphate (equimolar amounts) and triphenylsi-
lane (Si:Ir molar ratio=2) were reacted in CH2Cl2
(0.75 ml) under stirring. A vigorous formation of
methane was observed (l 0.20 ppm in CD2Cl2). Fer-
rocene was formed (l 4.18 ppm in CD2Cl2). After 1–2
h the reaction mixture was dried under vacuum. The
yellow oily residue was chromatographed on an alu-
mina column by eluting with pentane/benzene. The
eluted product was crystallized from dichloromethane/
pentane to give 2a (83%), 2b (81%), 2c (75%), 2d (70%)
as white crystals.

P. Di6ersi et al. / Journal of Organometallic Chemistry 593–594 (2000) 154–160
159
Table 3
Crystal data and structure refinement
Acknowledgements
This work was supported by the CNR (Rome).
Empirical formula
Formula weight
Temperature
C31H39FIrPSi
681.88
293(2) K
,
Wavelength
Crystal system
Space group
0.71073 A
Monoclinic
Cc
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Organomet. Chem. 2 (1988) 91. (b) H. Yamashita, M. Tanaka,
Bull. Chem. Soc. Jpn. 68 (1995) 403. (c) L. Rosenberg, M.D.
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117 (1995) 12478.
Unit cell dimensions
,
a (A)
14.066(3)
13.739(3)
15.918(2)
108.14(1)
2923.3(10)
4
1.549
4.687
1360
0.24×0.20×0.12
2.13–25.00
−15h516, −15k516,
−185l518
3176
,
b (A)
,
c (A)
i (°)
3
,
Volume (A )
Z
Dcalc (g cm−3
)
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm)
q Range for data collection (°)
Index ranges
Reflections collected
Independent reflections
Completeness to q=22.50°
Refinement method
2909 [Rint=0.0318]
49.9%
Full-matrix least-squares on
F2
Data/restraints/parameters
Goodness-of-fit a on F2
Final R indices a [I\2|(I)]
R indices a (all data)
2909/2/292
1.051
R1=0.0520, wR2=0.1281
R1=0.0669, wR2=0.1384
−0.04(3)
Absolute structure parameter
Largest difference peak and hole 2.458 and −2.343
−3
,
(e·A
)
a Goodness-of-fit={S[w(Fo2−Fc2)2]/(N−P)}0.5, where N and P are
the no. of observations and parameters, respectively; R1=SꢀꢀFoꢀ−
ꢀFcꢀꢀ/SꢀFoꢀ;
wR2={S[w(F2o−F2c)2]/S[w(Fo2)2]}0.5
;
w=1/[|2(F2o)+
(0.0750Q)2+38.34Q] where Q=[max(Fo2, 0)+2F2c]/3.
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M.J. Auburn, R.D. Holmes-Smith, S.R. Stobart, P.K. Bakshi,
T.S. Cameron, Organometallics 15 (1996) 3032.
try. The hydrogen atoms were introduced in calculated
positions as riding atoms in the last refinement cycles.
In the final cycles the heavy atoms were refined with
anisotropic thermal parameters. Details on the refine-
ment and some statistical reliability data are listed at
the bottom of Table 3.
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7888.
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4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC No. 124099 for compound 2a. A
full list of observed and calculated structure factors has
been deposited with the editor as supplementary mate-
rial and is available upon request. Geometric calcula-
tions have been made by means of the PARST-97
program [17].

160
P. Di6ersi et al. / Journal of Organometallic Chemistry 593–594 (2000) 154–160
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System, Version 2.1, Siemens Analytical X-ray Instruments Inc.,
Madison, WI, 1994.
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X-ray Instruments Inc., Madison, WI, 1992.
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.