Novel indenyl half-sandwich osmium(II) complexes. X-ray structure of [Os{=C=C(H)But}(η5-C9H7)(PPh 3)2][PF6]·OEt2

Article abstract of DOI:10.1016/S0020-1693(02)01450-0

Reaction of LiC₉H₇ with [OsBr₂(PPh₃)₃] gives the complex [Os(η⁵-C₉H₇)Br(PPh₃) ₂] (1). The analogous complex [Os(η⁵-C₉H

Full text of DOI:10.1016/S0020-1693(02)01450-0

Inorganica Chimica Acta 347 (2003) 99Á106
/
www.elsevier.com/locate/ica
Novel indenyl half-sandwich osmium(II) complexes.
Cꢀ
C(H)But}(h5-C9H7)(PPh3)2][PF6]×
X-ray structure of [Os{ꢀ
/
/
/
OEt2
Jose´ Gimeno a,*, Mercedes Gonzalez-Cueva a, Elena Lastra a, Enrique Perez-Carreno b,
˜
Santiago Garc´ıa-Granda b
a Departamento de Qu´ımica Orga´nica e Inorga´nica, Instituto de Qu´ımica Organometa´lica ‘Enrique Moles’ (Unidad Asociada al C.S.I.C.),
Facultad de Qu´ımica, Universidad de Oviedo, 33071 Oviedo, Spain
b Departamento de Qu´ımica F´ısica y Anal´ıtica, Facultad de Qu´ımica, Universidad de Oviedo, 33071 Oviedo, Spain
Received 22 April 2002; accepted 19 September 2002
Dedicated to Profesor Rafael Uso´n with great admiration for his outstanding contribution to modern Inorganic Chemistry
Abstract
Reaction of LiC9H7 with [OsBr2(PPh3)3] gives the complex [Os(h5-C9H7)Br(PPh3)2] (1). The analogous complex [Os(h5-
C9H7)I(PPh3)2] (2) is obtained from the metathesis reaction of [Os(h5-C9H7)Cl(PPh3)2] with NaI. The treatment of [Os(h5-
C9H7)X(PPh3)2] with NaOMe leads to the hydride derivative [Os(h5-C9H7)H(PPh3)2] (3) which can be protonated with HBF4 to
yield the cationic complex [Os(h5-C9H7)H2(PPh3)2][BF4] (4). Abstraction of the halide ligand in complexes [Os(h5-C9H7)X(PPh3)2]
with NaPF6 or AgBF4 followed by the treatment with NCMe or terminal alkynes yield complexes [Os(h5-
ꢁ
ꢃ
/
C9H7)(NCMe)(PPh3)2][BF4] (6) and [Os{ꢀ
/
COCH2(CH2)3C
H2}(h5-C9H7)(PPh3)2][PF6] (7), respectively. X-ray crystal structure of
the vinylidene derivative [Os{ꢀ
/
Cꢀ
/
C(H)tBu}(h5-C9H7)(PPh3)2][PF6] is reported along with variable temperature NMR studies.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Osmium complexes; Indenyl complexes; Half-sandwich complexes
1. Introduction
C9H7)L(PPh3)2][X] complexes (Lꢀ
/
H2, NCMe, Xꢀ
PF6). Structural stu-
Cꢀ
C(H)tBu}(h5-C9H7)-
/
ꢁ
ꢃ
/
BF4; Lꢀ
/
COCH2(CH2)3C
H2, Xꢀ
/
During the last few years we have extensively studied
the chemistry of indenyl half-sandwich ruthenium (II)
complexes [1,2] including alkynyl, vinylidene and allen-
ylidene derivatives. We have also reported the synthesis
of the first indenyl half-sandwich osmium complexes
containing the fragment ‘Os(h5-C9H7)(PPh3)2’ [3]. At
present the chemistry of the indenyl osmium complexes
is relatively much less known compared to that of the
corresponding ruthenium derivatives [4]. Due to this fact
we believed it of interest to extend the scope of the
indenyl osmium derivatives. Here we report the synthe-
sis and characterization of novel neutral [Os(h5-
dies on the complex [Os{ꢀ
/
/
(PPh3)2][PF6], including dynamic processes in solution
using NMR spectroscopy and its X-ray crystal structure,
are also reported.
2. Experimental
2.1. Materials and measurements
The reactions were carried out under dry nitrogen
using Schlenk techniques. All solvents were dried by
standard methods and distilled under nitrogen before
use. The complexes [OsX2(PPh3)3] were synthesized as in
C9H7)X(PPh3)2] (Xꢀ
(PPh3)L] (Lꢀ
/
Br, I, H), [Os(h5-C9H7)Br-
/
PMe3, PMe2Ph) and cationic [Os(h5-
reference [5] [Os(h5-C9H7)Cl(PPh3)2] and [Os{ꢀ
/
Cꢀ
/
C(H)tBu}(h5-C9H7)(PPh3)2][PF6] were previously de-
scribed [3]. LiC9H7 was prepared by modifications in a
published method [6] and stored in a dry box. C9H8,
* Corresponding author. Tel.: ꢁ
446.
E-mail address: jgh@sauron.quimica.uniovi.es (J. Gimeno).
/
34-985-103-461; fax: ꢁ34-985-103-
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(02)01450-0

100
J. Gimeno et al. / Inorganica Chimica Acta 347 (2003) 99Á106
/
LinBu, HBF4×
from Aldrich Chemical Co. Infrared spectra were
recorded on a PerkinÁElmer 1720-XFT spectrometer.
The C and H analyses were carried out with a PerkinÁ
/
OEt2 and AgBF4 were used as received
(C-2), 109.7 (C-3a,7a), 126.3 (Ind), 127.9Á
/140.4 (Ind,
Ph). Dd(C-3a,7a)ꢀ 21.0.
/
ꢂ
/
/
/
2.2.3. [Os(h5-C9H7)H(PPh3)2] (3)
Elmer 240-B microanalyzer. NMR spectra were re-
corded on a Bruker AC300 instrument at 300 (1H),
121.5 (31P) or 75.4 MHz (13C) and on a Bruker AC200
instrument at 200 (1H), 81.0 (31P) or 50.3 MHz (13C)
using SiMe4 or 85% H3PO4 as standards. The following
atom labels are used for the 1H and 13C{1H} NMR
spectroscopic data.
A solution of NaOMe prepared in situ stirring NaH
(0.192 g, 8 mmol) in MeOH (12 ml), was added to a
suspension of complex [OsCl(h5-C9H7)(PPh3)2] (343 mg,
0.40 mmol) in MeOH (50 ml) and the mixture was
refluxed for 1 hour. The solvent was evaporated and the
residue was extracted with diethyl ether and filtered with
Kieselguhr. The solvent was then removed in vacuo to
yield complex 3 (283 mg, 86%) as a yellow solid mixture
of two rotamers. Anal. Calc. for C45H38OsP2: C, 65.0;
H, 4.6. Found: C, 64.9; H, 4.5%. 31P{1H} NMR (C6D6):
1
d 17.21, 17.27; H NMR (C6D6): d ꢂ
/
17.83 (t, JHP
26.0 Hz, 1H, H), 4.57
(m, 4H, H-1,3), 5.77 (m, 2H, H-2), 6.01 (m, 4H, H-4,7 or
H-5,6), 6.87Á7.77 (m, 64H, H-4,7 or H-5,6 and Ph);
13C{1H} NMR (C6D6): d 67.6 (C-1,3), 67.7 (C-1,3), 82.2
(C-2), 106.5 (C-3a,7a), 123.4 (Ind), 123.8 (Ind), 127.8Á
142.7 (Ind, Ph). Dd(C-3a,7a)ꢀ
24.2. IR (KBr, cmꢂ1):
2158 (OsH).
ꢀ
/
26.0 Hz, 1H, H), ꢂ
/
17.82 (t, JHP
ꢀ
/
The parameter Dd(C-3a,7a) is defined as the differ-
ence between d(C-3a,7a) of the indenyl complex and
/
d(C-3a,7a) of sodium indenyl (dꢀ130.7 ppm). The term
/
/
‘Ind’ in the NMR data is used for the undefined signals
of the benzoid ring.
/
ꢂ
/
2.2.4. [Os(h5-C9H7)Br(PPh3)(PR3)] (PR3ꢀ
(4a), PMe2Ph (4b)
/PMe3
2.2. Synthesis
A solution of complex [OsBr(h5-C9H7)(PPh3)2] (100
mg, 0.11 mmol) and PR3 (0.48 mmol) in toluene (10 ml)
was heated at refluxing temperature for four hours. The
solvent was then evaporated and the residue was
extracted with diethyl ether and filtered through Kie-
selguhr. The solvent was then removed in vacuo and the
solid washed once with hexane (5 ml) and vacuum dried
2.2.1. [Os(h5-C9H7)Br(PPh3)2] (1)
A solution of [OsBr2(PPh3)3] (330 mg, 0.29 mmol) and
LiInd (70 mg, 0.58 mmol) in tetrahydrofuran (30 ml)
was stirred for 2 h at room temperature (r.t.). The
solvent was then evaporated and the residue was
extracted with diethyl ether, evaporated in vacuo and
the obtained solid washed once with hexane and vacuum
dried to yield complex 1 (209 mg, 79%) as an orange
solid. Anal. Calc. for C45H37BrOsP2: C, 59.4; H, 4.1.
to yield complexes 4a, b as brown solids. PR3ꢀ
(4a): 15% yield; 31P{1H} NMR (C6D6): d Á
42.40 (d,
JPP 15.0 Hz, PMe3), 5.82 (d, JPP
15.0 Hz, PPh3); 1H
NMR (C6D6): d 1.34 (d, JHP 9.4 Hz, PMe3), 3.87 (m,,
1H, H-2), 4.92 (m, 1H, H-1 or H-3), 4.97 (m, 1H, H-1 or
H-3), 6.66Á7.69 (m, 19H, H-4,7, H-5,6 and Ph);
13C{1H} NMR (C6D6): d 20.2 (d, JCP
37.2 Hz,
/PMe3
/
ꢀ
/
ꢀ
/
Found: C, 59.9; H, 4.3%. 31P{1H} NMR (C6D6): d ꢂ
2.23; 1H NMR (C6D6): d 4.53 (d, JHH
1.9 Hz, 2H, H-
7.93 (m,
/
ꢀ
/
ꢀ
/
1,3), 5.11 (t, JHH
ꢀ
/
1.9 Hz, 1H, H-2), 6.90Á
/
/
34H, H-4,7, H-5,6 and Ph); 13C{1H} NMR (C6D6): d
ꢀ
/
62.3 (C-1,3), 84.3 (C-2), 110.1 (C-3a,7a), 125.0 (Ind),
PMe3), 58.9 (C-1 or C-3), 61.8 (C-1 or C-3), 81.9 (C-
2), 110.2 (C-3a,7a), 110.3 (C-3a,7a), 125.5 (Ind), 127.2
127.4Á
/
139.3 (Ind, Ph). Dd(C-3a,7a)ꢀ
/
ꢂ20.6.
/
(Ind), 132.3-140.4 (Ind, Ph). Dd(C-3a,7a)ꢀ
PR3ꢀ
PMe2Ph (4b): 21% yield; 31P{1H} NMR (C6D6):
d ꢂ31.97 (d, JPP 13.1 Hz, PMe2Ph), 3.90 (d, JPP
13.1 Hz, PPh3); H NMR (C6D6): d 1.26 (d, JHP 9.9
Hz, PMe2Ph), 3.66 (m,, 1H, H-2), 4.51 (m, 1H, H-1 or
H-3), 4.70 (m, 1H, H-1 or H-3), 6.50Á7.74 (m, 24H, H-
4,7, H-5,6 and Ph).
/
ꢂ
/
20.5;
2.2.2. [Os(h5-C9H7)I(PPh3)2] (2)
/
A suspension of complex [Os(h5-C9H7)Cl(PPh3)2] (50
mg, 0.06 mmol) and NaI (17 mg, 0.12 mmol) in MeOH
(1 ml) was refluxed for three hours. The solvent was then
evaporated and the residue was extracted with diethyl
ether and filtered with Kieselguhr. The solvent was
removed in vacuo and the resulting solid washed with
hexane (2x 10 ml) and vacuum dried to yield complex 2
(57 mg, 61%) as an orange solid. Anal. Calc. for
C45H37IOsP2: C, 56.5; H, 3.9. Found: C, 56.1; H,
/
ꢀ
/
ꢀ
/
1
ꢀ
/
/
2.2.5. [Os(h5-C9H7)H2(PPh3)2][BF4] (5)
To a solution of complex [OsH(h5-C9H7)(PPh3)2] (3)
(100 mg, 0.12 mmol) in diethyl ether (20 ml), HBF4×
/
4.0%. 31P{1H} NMR (C6D6): d ꢂ
(C6D6): d 4.51 (d, JHH 2.2 Hz, 2H, H-1,3), 4.93 (t,
JHH 2.2 Hz, 1H, H-2), 6.22Á7.41 (m, 34H, H-4,7, H-
5,6 and Ph); 13C{1H} NMR (C6D6): d 63.8 (C-1,3), 85.9
/
4.26; 1H NMR
OEt2 (0.12 mmol) in diethyl ether (20 ml) was added
dropwise at ꢂ80 8C and the mixture was stirred until
r.t. was reached. Solvents were then decanted and the
solid residue washed with diethyl ether (2ꢃ10 ml) and
ꢀ
/
/
ꢀ
/
/
/

J. Gimeno et al. / Inorganica Chimica Acta 347 (2003) 99Á
/106
101
vacuum dried to yield complex 5 (102 mg, 92%) as a grey
solid. Anal. Calc. for C45H39BF4OsP2: C, 58.8; H, 4.3.
2.2.8. X-ray diffraction studies of [Os{ꢀ
/
Cꢀ
/
C(H)tBu}-
(h5-C9H7)(PPh3)2][PF6]
Found: C, 58.2; H, 4.2%. 31P{1H} NMR (C6D6): d
Data collection, crystal, and refinement parameters
are collected in Table 1. The unit-cell parameters were
obtained from the least-squares fit of 25 reflections with
u between 10 and 138. The intensity data were measured
1
11.80; H NMR (C6D6): d ꢂ
/
11.69 (t, JPH
ꢀ31.4 Hz,
/
2H, H), 4.95 (t, JHH
ꢀ
/
2.5 Hz, 1H, H-2), 5.39 (d, JHH
ꢀ
/
2.5 Hz, 2H, H-1,3), 6.68 (m, 2H, H-4,7 or H-5,6), 6.77Á
/
7.49 (m, 32H, H-4,7 or H-5,6 and Ph); 13C{1H} NMR
(C6D6): d 76.9 (C-1,3), 83.0 (C-2), 107.2 (C-3a,7a), 124.4
using the v Á2u scan technique and a variable scan rate,
/
with a maximum scan time of 60 s per reflection. The
final drift correction factors were between 0.98 and 1.02.
On all reflections, profile analysis [7,8] was performed.
Lorentz and polarization corrections were applied, and
the data were reduced to Fo2 values.
(Ind), 128.7Á
/
134.7 (Ind, Ph). Dd(C-3a,7a)ꢀ
/
ꢂ23.5. IR
/
(KBr, cmꢂ1): 2116 (OsH), 2079 (OsH), 1085 (BF4ꢂ).
The structure was solved by Patterson methods and
phase expansion using the program DIRDIF [9], and
refined by least-squares using SHELXL-93 [10]. The
hydrogen atoms were geometrically placed.
During the final stages of the refinement, the posi-
tional parameters and the anisotropic thermal para-
meters of the non-H atoms were refined except to the
high disordered molecule of ether which was refined as a
rigid model with a common isotropic thermal parameter
to carbon atoms. The hydrogen atoms were isotropically
refined with a common thermal parameter to each
2.2.6. [Os(h5-C9H7)(NCMe)(PPh3)2][BF4] (6)
Complex [Os(h5-C9H7)Cl(PPh3)2] (100 mg, 0.12
mmol) and AgBF4 (25 mg, 0.13 mmol) in acetonitrile
(20 ml) were stirred in absence of light at r.t. for 1 h.
Solvent was then removed under reduced pressure and
the solid residue was extracted with dichloromethane
and filtered through Kieselguhr. Dichloromethane was
removed in vacuo and the solid washed with diethyl
ether (2ꢃ15 ml) and vacuum dried to yield complex 6
/
(61 mg, 55%) as a brown solid. Anal. Calc. for
C47H40BF4NOsP2: C, 58.9; H, 4.2; N, 1.5. Found: C,
58.6; H, 4.1; N, 1.4%. 31P{1H} NMR (C6D6): d 3.09; 1H
NMR (CDCl3): d 2.48 (s, 3H, Me), 4.78 (m, 2H, H-1,3),
Table 1
Crystal data and structure refinement for [Os{ꢀ
C9H7)(PPh3)2][PF6]
/
Cꢀ
/
C(H)tBu}(h5-
4.84 (m, 1H, H-2), 6.85Á
Ph); 13C{1H} NMR (C6D6): d 4.5 (Me), 64.0 (C-1,3),
89.1 (C-2), 108.1 (C-3a,7a), 124.4 (Ind), 128.2Á135.5
22.6. IR (KBr,
/7.37 (m, 34H, H-4,7, H-5,6 and
Empirical formula
Formula weight
Temperature (K)
C55H57F6OOsP3
1131.12
293(2)
/
(NCMe, Ind, Ph). Dd(C-3a,7a)ꢀ
/
ꢂ
/
cmꢂ1): 2264 (Cꢄ
/
N), 1054 (BF4ꢂ).
˚
Wavelength (A)
0.71073
monoclinic
P21/c
Crystal system
Space group
Unit cell dimensions
ꢁ
ꢃ
˚
a (A)
13.043(4)
19.75(2)
19.223(6)
90
2.2.7. [Os{ꢀ
[PF6] (7)
A mixture of [Os(h5-C9H7)Cl(PPh3)2] ( (120 mg, 0.14
mmol), NaPF6 (94 mg, 0.56 mmol) and HCꢀ
/
COCH2(CH2)3C
/
H2}(h5-C9H7)(PPh3)2]-
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
90.35(3)
90
/
C(CH2)3CH2OH (69 mg, 0.70 mmol) in methanol (10
ml) was heated under reflux for 4 h. After evaporation
to dryness at reduced pressure the residue was extracted
with dichloromethane and filtered through Kieselguhr.
The solvent was then removed in vacuo and the solid
3
˚
V (A )
4951(6)
4
Z
Dcalc (Mg mꢂ3
)
1.518
2.734
2280
Absorption coefficient (v)
F(000)
Crystal size (mm3)
0.26ꢃ
25.98
165h 5
05l 523
9697
9697 [Rint
25.988 (%) 99.9
/
0.23ꢃ
/
0.19
washed with diethyl ether (2ꢃ
to give complex 7 as a brown solid (76 mg, 51% yield).
31P{1H} NMR (CDCl3): d ꢂ0.94; 1H NMR (CDCl3): d
1.08 (m, 2H, CH2), 1.50 (m, 2H, CH2), 1.85 (m, 2H,
CH2), 3.03 (m, 2H, OCH2 or ꢀCCH2), 3.12 (m, 2H,
OCH2 or ꢀCCH2), 5.26 (m, 2H,, H-4,7 or H-5,6), 5.42
7.68 (m, 32H,
/10 ml) and vacuum dried
Theta Range for data collection (8) 1.48Á
Index ranges
/
ꢂ/
/
/
16, 05
/
k 524,
/
/
/
/
Reflections collected
Independent reflections
ꢀ0.0871]
/
/
Completeness to thetaꢀ
Absorption correction
Max. and min. transmission
Refinement method
/
/
empirical
0.6246 and 0.5367
full-matrix least-squares on F2
(m, 2H, H-1,3), 6.17 (m, 1H, H-2), 6.70Á
/
H-4,7or H-5,6 and Ph); 13C{1H} NMR (CDCl3): d 20.3
(CH2), 27.4 (CH2), 28.8 (CH2), 59.7 (CH2), 75.2 (C-1,3),
77.4 (OCH2), 95.2 (C-2), 114.2 (C-3a,7a), 123.6 (Ind),
Data/restraints/parameters
Goodness-of-fit on F2
9697/0/558
0.992
Final R indices [I ꢁ
R indices (all data)
Largest difference peak and hole
/
2s(I)]
R1ꢀ
R1ꢀ
1.796 and ꢂ
/
0.0537, wR2ꢀ
0.1998, wR2ꢀ
2.036
/
0.1147
0.1631
124.4Á
Dd(C-3a,7a)ꢀ
838 (PF6ꢂ).
/
136.2 (Ind, Ph), 257.4 (t, JCP
ꢀ
/
7.6 Hz, Ca).
/
/
/
ꢂ
/
16.6. IR (KBr, cmꢂ1): 1239 (CO),
/
ꢂ3
˚
(e A
)

102
J. Gimeno et al. / Inorganica Chimica Acta 347 (2003) 99Á106
/
group of hydrogen atoms riding to the same carbon
atom. The function minimized was [Sw(Fo2ꢂFc2)2/
S w(Fo2)2]1/2 1/[s2(Fo2)ꢁ(0.0605P)2ꢁ
wꢀ (0.00P)]
where Pꢀ
(max(Fo2,O)ꢁ2Fc2)/3 with s(Fo2)2 from
counting statistics. The maximum shift to e.s.d. ratio
in the last full-matrix least-squares cycle was 0.02. The
(see Section 2 for details). Significantly, NMR spectra at
room temperature indicate the existence of two rotamers
in solution. Thus, H NMR spectrum shows two triplet
/
1
,
/
/
/
/
/
hydride resonances at high field (d ꢂ
/
17.82 and Á17.83
/
ppm, JPH
ꢀ
/
26.0 Hz). 31P NMR spectrum which dis-
plays two resonances at d 17.21 and 17.27 ppm, is also
in agreement with the presence of two rotamers. They
arise from the formally cis and trans orientations of the
benzo ring of the indenyl group with respect to the
hydride ligand (Fig. 1). Similar rotamers have been
final difference Fourier map showed no peaks higher
ꢂ3
˚
than 1.80 e A
/
2.04 e Aꢂ3; most of
˚
or deeper than ꢂ
the highest peaks were found near to the disordered
ether molecule.
described for the complexes [Ru(h5-C9H7)I(CO)(PR3)]
Atomic scattering factors were taken from reference
[11]. Geometrical calculations were made with PARST
[12]. The figure showing the coordination and the
atomic numbering scheme was drawn by EUCLID [13].
All calculations were performed at University of Oviedo
on the Scientific Computer Center and X-ray group
DEC-ALPHA computers.
1
Rꢀi
/
Pr, Cy [14]. Variable temperature 31P{1H} and H
NMR spectra up to ca. 80 8C remain practically
unchanged indicating that the rotation is not allowed
within this temperature range. This is probably due to
the steric hinderance of the PPh3 ligands which block the
complete rotation of the indenyl ring.
3. Results and discussion
3.1. Synthesis of [Os(h5-C9H7)X(PPh3)2] Xꢀ
I (2), H (3)
/
Br (1),
Following the reported synthetic approach to [Os(h5-
C9H7)Cl(PPh3)2] [3], the bromide derivative (1) is
prepared from the reaction of [OsBr2(PPh3)3], with
LiC9H7 in tetrahydrofurane (79%). (Eq. (1))
Fig. 1. Representation of the two rotamers of [Os(h5-C9H7)H(PPh3)2].
Attempts to use this complex in typical insertion
reactions have failed. Thus, complex 3 does not react
with MeO2CCꢄ
/
CCO2Me in refluxing toluene recovering
LiC9H7
0
[OsBr2(PPh3)3]
[Os(h5-C9H7)Br(PPh3)2]
(1)
the starting material unchanged after 4 h. The inertness
of complex 3 is in accord with the observed unreactivity
of the analogous ruthenium complex [Ru(h5-
C9H7)H(PPh3)2] towards terminal and internal alkynes.
We have reported that the presence of small bite ligands
favours the insertion as observed for the complex
[Ru(h5-C9H7)H(dppm)] [15].
THF
1
Treatment of [Os(h5-C9H7)Cl(PPh3)2] with an excess
of NaI in refluxing methanol affords complex 2 (61%)
(Eq. (2)). Complexes 1 and 2 are isolated as orange air-
stable crystalline solids and fully characterized by
elemental analyses and spectroscopic methods (see
Section 2). The spectroscopic data can be compared to
those reported for the parent chloride complex [3] and
therefore, they will not be further discussed.
3.2. Synthesis of [Os(h5-C9H7)Br(PPh3)L] (Lꢀ
(4a); PMe2Ph (4b))
/PMe3
NaI
0
[Os(h5-C9H7)Cl(PPh3)2]
[Os(h5-C9H7)I(PPh3)2] (2)
We have previously reported that [Ru(h5-C9H7)-
Cl(PPh3)2] is able to undergo phosphine exchange
reactions which proceed through a dissociative pathway
with rate constants one order higher in magnitude than
those of the corresponding cyclopentadienyl derivatives.
This has been attributed to a type of dissociative indenyl
effect [16]. In order to check this kinetic effect in osmium
complexes, ligand exchange processes have been studied
using the parent complexes [Os(h5-C9H7)X(PPh3)2].
Thus, the treatment of [Os(h5-C9H7)Br(PPh3)2] (1)
with PMe3 and PMe2Ph in refluxing toluene for 4 hours
gives complexes 4a (15%) and 4b (21%). In contrast,
heating under reflux a toluene solution of [Os(h5-
C9H7)Cl(PPh3)2] leads to decomposition products or
remains unchanged in the presence of an excess of PR3
MeOH
2
One of the most efficient synthetic methods for
transition metal hydrides is that using sodiumalkoxides
bearing b-hydrogen atoms as a hydrogen transfer agent.
Thus, the reaction of complex [Os(h5-C9H7)Cl(PPh3)2]
with NaOMe in methanol yields the hydride derivative
[Os(h5-C9H7)H(PPh3)2] (3) which is isolated as a yellow
solid in 86% yield after work-up (Eq. (3)).
NaOMe=MeOH
[Os(h5-C9H7)Cl(PPh3)2]
ꢂNaCl; ꢂH2CO
[Os(h5-C9H7)H(PPh3)2]
(3)
3
Elemental analyses, IR and NMR spectroscopy data
of 3 are in accordance with the proposed formulation.

J. Gimeno et al. / Inorganica Chimica Acta 347 (2003) 99Á
/106
103
at room temperature. The characterization of complexes
4a and 4b is supported by elemental analyses and the
standard spectroscopic techniques (see Section 2 for
details). Although no kinetic studies have been per-
formed we note that analogous phosphine exchange
reactions starting from [Os(h5-C5H5)Br(PPh3)2] require
12 h in refluxing toluene [17] indicating that the indenyl
kinetic effect is operative [18].
follows unequivocally from its reactivity, we have now
been able to isolate it in the presence of acetonitrile
giving rise quantitatively to the adduct [Os(h5-
C9H7)(NCMe)(PPh3)2][BF4] (6) (Eq. (5)).
AgBF4
0
[Os(h5-C9H7)Cl(PPh3)2]
NCMe
[Os(h5-C9H7)(NCMe)(PPh3)2][BF4]
(5)
6
All attempts to displace the co-ordinated acetonitrile
by typical two electron ligands such as CO and
monodentate phosphines have been unsuccessful.
In a previous paper [3] we have described the synthesis
3.3. Synthesis of cationic complexes [Os(h5-C9H7)L-
(PPh3)2][X]
3.3.1. Synthesis of [Os(h5-C9H7)H2(PPh3)2][BF4] (5)
As expected for the typical electron richness of
analogous hydride derivatives [19], the addition of
tetrafluoroboric acid to a solution of 3 in diethyl ether
ꢁ
ꢃ
of the oxacycliccarbenes [Os{ꢀ
C9H7)(PPh3)2][PF6] (nꢀ1, 2) which are obtained from
the reaction of [Os(h5-C9H7)Cl(PPh3)2] with v-hydro-
xyalk-1-ynes, HCꢄC(CH2)nCH2OH (nꢀ1, 2) and
NaPF6. However, the reaction with 5-hexin-1-ol (nꢀ
3) does not proceed in the same way giving instead the
/
COCH2(CH2)nC
/
H2}(h5-
/
/
/
at ꢂ80 8C leads, to the precipitation of the desired
/
/
cationic complex [Os(h5-C9H7)H2(PPh3)2][BF4] (5) (Eq.
(4)).
intermediate hydroxivinylidene complex [Os{ꢀ
/
Cꢀ
/
HBF4+OEt2
[Os(h5-C9H7)H(PPh3)2]
Et2O
C(H)(CH2)3CH2OH}(h5-C9H7)(PPh3)2][PF6]. We have
now succeeded in converting this specie in the final
[Os(h5-C9H7)H2(PPh3)2][BF4]
(4)
ꢁ
ꢃ
oxacyclic carbene [Os{ꢀ
/
COCH2(CH2)3C/
H2}(h5-C9H7)-
(PPh3)2][PF6] (7) which is formed via intramolecular
cyclization of the hydroxivinylidene complex (Eq. (6)).
5
Complex 5 can be easily identified as the dihydride
derivative on the basis of the spectroscopic data. Thus,
NaPF6=MeOH
[Os(h5-C9H7)Cl(PPh3)2]
HCꢄC(CH2)3CH2OH
the IR spectrum displays n(OsÁ
and 2079 cmꢂ1. 1H NMR shows a triplet resonance at d
11.69 (JPH 31.4 Hz) which is consistent with a trans
/H) absorptions at 2116
ꢁ
ꢃ
[OsfꢀCOCH2(CH2)3CH2g(h5-C9H7)(PPh3)2][PF6] (6)
Complexes 6 and 7 have been characterized by IR and
NMR spectroscopy and analytical methods (see Section
ꢂ
/
ꢀ
/
arrangement of the two hydride ligands. A similar
geometry has been described for the analogous com-
plexes [Os(h5-C5H5)H2(PPh3)2]ꢁ (d ꢂ
/
11.3 JPH
Hz) [17,20] and [Os(h5-C5H5)H2(CO)(PiPr3)]ꢁ (d
11.4 JPH 28.8 Hz) [21].
Analogous dihydride cyclopentadienyl complexes
22] have been reported
ꢀ29
/
2 for details). Relevant features are: (a) the weak n(Cꢀ
/
N) absorption at 2264 cmꢂ1 in the IR spectrum of 6; (b)
a singlet signal at in the 31P{1H} NMR spectrum of 7
indicating the chemical equivalence of the phosphines.
This is consistent with the free rotation of the carbene
group around the ruthenium carbene bond; (c) the
characteristic low-field carbenic Ca resonance (d 311.5
ppm) which appears as a triplet due to the coupling to
the two equivalent phosphorous nuclei.
ꢂ
/
ꢀ
/
[Os(h5-C5H5)H2(PR3)2]ꢁ [17,20Á
/
to be formed through a transient dihydrogen derivative.
To find out whether an intermediate dihydrogen species
1
is formed the addition of acid was monitored by H
NMR at low temperature (ꢂ78 8C). However, no
/
further signals besides those assigned to complex 5, are
observed. This fact probably arises from the electronic-
rich nature of the metallic fragment which determines
the favourable stabilization of the dihydride complex.
[22]
3.4. Structural studies of [Os{ꢀ
/
Cꢀ
/
C(H)tBu}(h5-
C9H7)(PPh3)2][PF6] in solution and in the solid state
The preferred conformation of the indenyl ring in
half-sandwich metal complexes have been the subject of
longstanding studies both in solution and solid state [4].
We have reported that the orientation of the indenyl
ligand with respect to the vinylidene, alkynyl, alkenyl
and allenylidene groups (formally cis or trans) in
ruthenium(II) complexes is clearly dependent on the
nature of the unsaturated hydrocarbon groups. In order
to have comparative information between ruthenium
and osmium vinylidene derivatives, we have performed
structural studies on the conformational features of the
3.3.2. Synthesis of [Os(h5-C9H7)(NCMe)(PPh3)2]-
ꢁ
ꢃ
[BF4] (6) and [Os{ꢀ
/
COCH2(CH2)3C
H2}(h5-
/
C9H7)(PPh3)2][PF6] (7)
We have extensively used the ability of the indenyl
complexes in the activation of terminal alkynes via in
situ generation of the sixteen electron species [M(h5-
C9H7)(PPh3)2]ꢁ (Mꢀ
Ru, Os) [4]. These unsaturated
/
species are easily prepared from the parent chloride
complexes by reaction with an appropriate chloride
abstractor. Although the formation of this species

104
J. Gimeno et al. / Inorganica Chimica Acta 347 (2003) 99Á106
/
Fig. 2. Perspective view of the structure of the cationic complex [Os{ꢀ
/
Cꢀ
C(H)tBu}(h5-C9H7)(PPh3)2]ꢁ. Ph groups have been omited for clarity.
/
indenyl ligand in the vinylidene complex [Os{ꢀ
/
Cꢀ
/
3.4.2. X-ray crystal structure of [Os{ꢀ
/
Cꢀ
/
C(H)tBu}-
C(H)tBu}(h5-C9H7)(PPh3)2][PF6] [3].
(h5-C9H7)(PPh3)2][PF6]
A view of the molecular geometry is shown in Fig. 2.
Selected bond distances and angles are listed in Table 2.
3.4.1. NMR studies
The room-temperature 31P{1H} NMR spectrum
shows one singlet resonance at d ꢂ6.8 ppm indicating
/
Table 2
Selected bond lengths and slip parameter D (A) and bond angles and
˚
the chemical equivalence of the two phosphorus atoms.
This is consistent with the existence of two simultaneous
dynamic processes in solution, both of them rapid on
the NMR time scale: (a) the rotation of the vinylidene
dihedral angles FA, HA, DA and CA (8) for [Os{ꢀ
/
Cꢀ
/
C(H)tBu}(h5-
C9H7)(PPh3)2][PF6]
Bond lengths
OsÁ
OsÁ
OsÁ
OsÁ
/
C*
1.981(7)
2.365(3)
2.313(3)
1.841(13)
C(1)Á
/
C(2)
1.343(16)
1.536(16)
0.12(1)
group around the Ruꢀ
/
C bond; and (b) the rotation of
/
P(1)
P(2)
C(1)
C(2)Á
/
C(3)
the indenyl ring.
Variable temperature 31P{1H} NMR experiments
show that the singlet resonance observable in the spectra
a
/
D
/
Bond angles
OsÁC(1)ÁC(2)
C(1)ÁC(2)Á
C(1)ÁC(2)Á
C(3)ÁC(2)Á
P(2)ÁOsÁ
C(1)ÁOsÁ
C(1)ÁOsÁ
at room temperature (d ꢂ
broad singlets at d 0.68 and ꢂ
The coalescence temperature is in the range 228Á
/
6.8 ppm) gives rise to two
9.80 ppm below 208 K.
208 K
/
/
162.1(11)
129.7(13)
115.1
C(1)Á
P(1)ÁOsÁ
OsÁ
/
OsÁ
/C*
120.2(4)
120.75(8)
120.95(8)
53.4(7)
63.8(3)
10.0(1)
5.0(1)
/
/
/
C(3)
H(2)
H(2)
/
/C*
/
/
P(2)Á
/
/C*
/
/
/
115.1
DA b
CA c
FA d
HA e
with an estimated energy barrier DG# in the range 8.8Á
/
/
/
P(1)
97.08(11)
97.7(4)
94.2(4)
9.7 kcal molꢂ1 [23].1 Since only a single coalescence
temperature was observed, it is not possible to distin-
guish whether one or both of the two possible fluxional
processes have been frozen [24].2
/
/P(1)
/
/P(2)
a
Dꢀ
/
d(OsÁ
/
C(74),C70))Á/d(OsÁ
/
C(71),C(73)).
b
DA (dihedral angle)ꢀ
/angle between normals to least-squares
planes defined by C*, Os, C(1) and Os, C(1), C(2), C(3).
c
CA (conformational angle)ꢀ
squares planes defined by C**, C*, Os and C*, Os, C(1). C*ꢀ
centroid of C(70), C(71), C(72), C(73) and C(74).C**ꢀC(70), C(74),
C(75), C(76), C(77), C(78).
/
angle between normals to least-
/
1
Estimated from the coalescence temperature using the Eyring
/
equation.
2
d
Rotation of the vinylidene ligand at room temperature is well
9 kcal molꢂ1) and extend
FA (fold angle)ꢀangle between normals to least-squares planes
/
stablished, having similar energy barriers (7Á
¨
/
defined by C(71), C(72), C(73) and C(70), C(74), C(75), C(76), C(77),
C(78).
Huckel calculations for the model [Os(h5-C H )(PH ) (ꢀ
/
Cꢀ
show a rotation barrier for the rotation of the indenyl ring of 6.46 kcal
molꢂ1
/
CH2)]ꢁ
9
7
3 2
e
HA (hinge angle)ꢀangle between normals to least-squares planes
/
.
defined by C(71), C(72), C(73) and C(71),C(74), C(70), C(73).

J. Gimeno et al. / Inorganica Chimica Acta 347 (2003) 99Á
/106
105
ruthenium
(PPh3)2]ꢁ (CAꢀ
(h5-C9H7)(PPh3)2]ꢁ (CAꢀ
derivatives
[Ru(ꢀ
/
Cꢀ
/
CMe2)(h5-C9H7)-
/
157.8(4)8) [25] and [Ru{ꢀ
/
Cꢀ
/
CH(Ph)}-
/
164.6(3)8) [4], show the
benzo ring and the vinylidene ligand in a trans disposi-
tion (Fig. 3(a)).
As shown by the space filling representation of [Os-
{ꢀ
/
Cꢀ
C(H)tBu}(h5-C9H7)(PPh3)2][PF6] (Fig. 4), the in-
/
denyl ligand and the vinylidene chain do not show steric
interactions. However, the model shows that the indenyl
ring and the phenyl groups of the phosphines are
sterically hindered. On the basis of this fact, we propose
a limited rotation of the indenyl ring above the
vinilydene chain between the two phosphines (Fig.
3(b)). This disposition for the indenyl ligand can also
explain the inertness of the osmium vinilydenes towards
alcohols [3] since the Ca is protected by the indenyl
ligand.
Fig. 3. Representation of cis and trans rotamers for the cation [Os{ꢀ
/
Cꢀ .
C(H)tBu}(h5-C9H7)(PPh3)2]ꢁ
/
The unit cell consists of [Os{ꢀ
/
Cꢀ
/
C(H)tBu}(h5-C9H7)-
(PPh3)2]ꢁ cations, hexafluorophosphate anions and one
diethyl ether molecule. The indenyl ligand exhibits the
usual allylene h5 coordination type in the pseudoocta-
hedral three-legged piano-stool geometry around the
ruthenium atom. The interligand angles (94.2(4),
97.08(11) and 97.7(4)8) and those between the centroid
C* and the legs (120.2(4), 120.75(8) and 120.95(8)8)
show values typical of a pseudooctahedron.
The dihedral angle DA between the planes C* and
Os,Cl(1),Os,C(1),C(2),C(3) of 53.4(7)8 shows that the
orientation of the vinylidene chain is largely deviated
from the horizontal position (DAꢀ908) which is the
/
most favourable according theoretical calculations [26].
This deviation probably arises from the steric interac-
tions between the substituents of the vinylidene group
and the phenyl groups of the phosphine ligands.
The most relevant feature concerning the indenyl ring
is the conformational angle CA (CAꢀ
/
63.8(3)8), defined
The angle OsÁ
(162.1(11)8) is slightly smaller than for the cyclopenta-
dienyl derivative [Os(h5-C5Me5)(CO)(PPh3)2{ꢀ
Cꢀ
C(H)tBu}]ꢁ (175.08) [27], but the distances OsÁ
C(1)
and C(1)ÁC(2) are comparable in both derivatives.
/
C(1)ÁC(2) in the vinylidene moiety
/
between the planes C**ÁC*,Os and C*,Os,C(1) for
/
benzo ring cis to the vinylidene). This value shows a
trans orientation of benzo ring with respect to the
triphenylphosphine ligand. However, analogous indenyl
/
/
/
/
Fig. 4. Van der Waals representation for the cation [Os{ꢀ
/
Cꢀ .
C(H)tBu}(h5-C9H7)(PPh3)2]ꢁ
/

106
J. Gimeno et al. / Inorganica Chimica Acta 347 (2003) 99Á106
/
[6] W. Spaleck, M. Antberg, J. Rohrmann, A. Winter, B. Bachmann,
P. Kiprof, J. Behm, W.A. Herrmann, Angew. Chem., Int. Ed.
Engl. 31 (1992) 1347.
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 198991 . Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2
[7] D.F. Grant, E.J. Gabe, J. Appl. Crystallogr. 11 (1978) 114.
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DIRDIF Program System, Technical report, Crystallographic
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Acknowledgements
[13] A.L. Spek, The EUCLID package, in: D. Sayre (Ed.), Computa-
tional Crystallography, Clarendon Press, Oxford, 1982, p. 528.
[14] M.P. Gamasa, J. Gimeno, C. Gonzalez Bernardo, Unpublished
results.
Financial support by the Spanish Direccio´n General
de Investigacio´n Cient´ıfica y Te´cnica (project PB96-
0558) and Ministerio de Ciencia y Tecnolog´ıa (project
MCT-00-BQU-0227) is acknowledged. M.G. thanks the
Spanish Ministerio de Educacio´n y Ciencia for a
scholarship.
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Bernardo, B. Martin-Vaca, Organometallics 16 (1997) 5470.
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