Stable carbeneiridium(I) complexes with 16- and 18-electron configurations at the metal center

Article abstract of DOI:10.1021/om980984p

Using the mixed phosphine-stibine compound [IrCl(C2H4)(PiPr3)(SbiPr3)J (2) as the starting material, the square-planar carbeneiridium(I) complexes PrCl(=CRa)(PiIs)(SbiPrs)J (3a,b) and trans-PrCl(= CRz)(PiPr3)2] (4a,b) were prepared. The cyclopentadienyl d

Full text of DOI:10.1021/om980984p

9
52
Organometallics 1999, 18, 952-954
Sta ble Ca r ben eir id iu m (I) Com p lexes w ith 16- a n d
1
8-Electr on Con figu r a tion s a t th e Meta l Cen ter
Dagmara A. Ortmann, Birgit Webernd o¨ rfer, J an Sch o¨ neboom, and
Helmut Werner*
Institut f u¨ r Anorganische Chemie, Universit a¨ t W u¨ rzburg, Am Hubland,
D-97074 W u¨ rzburg, Germany
Received December 4, 1998
Sch em e 1a
Summary: Using the mixed phosphine-stibine com-
pound [IrCl(C2H4)(PiPr3)(SbiPr3)] (2) as the starting
material, the square-planar carbeneiridium(I) complexes
[IrCl(dCR2)(PiPr3)(SbiPr3)] (3a ,b) and trans-[IrCl(d
CR2)(PiPr3)2] (4a ,b) were prepared. The cyclopentadienyl
derivative [C5H5Ir(dCPh2)(PiPr3)] (5), obtained from 3a
and NaC5H5, reacts with HCl by attack of the IrdCPh2
bond; in contrast, upon treatment of 4a with HCl or
HBF4, hydridoiridium(III) complexes 8 and 9 with an
intact IrdCPh2 unit are formed.
Following the discovery that carbenerhodium(I) com-
plexes of the general composition trans-[RhCl(dCRR′)-
1
(
L)2] (L ) PR3, AsR3, SbR3) are readily accessible and
provide a rich chemistry including novel C-C coupling
reactions, we set out to prepare the iridium counter-
a
a : R ) C
6
H
5
6 4
. b: R ) p-C H Me.
2
parts. Since the methodology to obtain the square-
planar rhodium carbenes trans-[RhCl(dCRR′)(L)2] is
based on the use of the bis(stibine) compound trans-
proceeds cleanly and affords the carbene complexes 3a ,b
5
in 60-70% isolated yield. The most characteristic
spectroscopic feature of 3a and 3b is the signal for the
1
,2
[RhCl(C2H4)(SbiPr3)2] as the starting material,
we
1
3
carbene carbon atom in the C NMR spectrum at δ
40.9 (3a ) and 244.7 (3b), which is split into a doublet
due to P-C coupling.
initially attempted to generate the analogous carbe-
neiridium(I) complexes also from a precursor containing
two SbiPr3 ligands. However, these experiments failed.
Although the bis(stibine) derivative [IrCl(C2H4)2(SbiPr3)2]
reacts with PhCtCPh and Me3SiCtCSiMe3 by ligand
exchange to give the four-coordinate alkyne- and vi-
nylideneiridium(I) complexes trans-[IrCl(PhCtCPh)-
2
1
,2
In agreement with previous findings, the M-SbiPr3
bond in 3a ,b is more readily dissociable, and therefore
the mixed phosphine-stibine derivatives react smoothly
with PiPr3 to give the bis(phosphine) iridium carbenes
6
4
a and 4b, respectively. Both complexes, which are
(
SbiPr3)2] and trans-[IrCl{)CdC(SiMe3)2}(SbiPr3)2] in
thermally more stable than the precursors 3a ,b, have
3
excellent yield, it is completely inert toward Ph2CN2
under the same conditions. Therefore, the development
of an alternative preparative route was necessary. Here
we report the preparation, structure determination, and
preliminary reactivity studies of both square-planar and
half-sandwich-type iridium complexes that contain Ird
C(aryl)2 as a molecular unit.
been characterized by elemental analysis and spectro-
7
scopic techniques. The resonance for the IrdCR2 car-
1
3
bene carbon atom appears in the C NMR spectra of
(
4) The preparation of 2 is as follows. A suspension of 1 (105 mg,
.13 mmol) in 5 mL of pentane was treated under continuous stirring
with SbiPr (52 µL, 0.25 mmol). After benzene (5 mL) was added, the
0
3
more volatile materials (mainly pentane) were removed in vacuo. The
generated orange solution was stirred for 30 min and then brought to
dryness in vacuo. The bright orange solid was washed twice with 2
mL of pentane and dried: yield 159 mg (95%); mp 88 °C dec.
The synthetic pathways to obtain the carbeneiridium-
(I) compounds 3 and 4 are outlined in Scheme 1. The
key to success was the use of the mixed phosphine-
stibine complex 2 as the starting material, which was
isolated upon treatment of the binuclear precursor 1 and
(5) The preparation of 3a is as follows. A solution of 2 (121 mg, 0.18
mmol) in 10 mL of benzene was treated with Ph CN (35 mg, 0.18
2
2
mmol) at room temperature and then stirred under slightly reduced
pressure for 1 h. The solvent was removed, and the residue was
recrystallized from acetone at -78 °C. A brown microcrystalline solid
was obtained, which was washed twice with 1 mL of acetone (0 °C)
and dried: yield 105 mg (72%); mp 42 °C dec. Compound 3b was
2
equiv of SbiPr3 as a bright orange solid in nearly
4
quantitative yield. While compound 2 can be stored
under argon at -30 °C for weeks, it is labile in solution
and decomposes particularly in CH2Cl2 quite rapidly.
The reaction of 2 with N2CR2 (R ) Ph, p-Tol) in benzene
prepared analogously, using 2 (112 mg, 0.17 mmol) and N
Me) (38 mg, 0.17 mmol) as starting materials: dark brown solid; yield
3 mg (59%); mp 24 °C dec.
6) The preparation of 4a is as follows. A solution of 3a (200 mg,
0.28 mmol) in 20 mL of pentane was treated with PiPr (55 µL, 0.28
2 6 4
C(C H -p-
2
8
(
(
1) Schwab, P.; Mahr, N.; Wolf, J .; Werner, H. Angew. Chem. 1993,
3
1
05, 1498-1500; Angew. Chem., Int. Ed. Engl. 1993, 32, 1480-1482.
(
Werner H.; Schwab, P.; Bleuel, E.; Mahr, N.; Steinert, P.; Wolf, J .
Chem. Eur. J . 1997, 3, 1375-1384. (c) Bleuel, E. Dissertation,
Universit a¨ t W u¨ rzburg, to be submitted.
mmol) and stirred for 45 min at room temperature. The solvent was
removed, and the residue was recrystallized from acetone at -78 °C.
A brown, moderately air-stable solid was obtained, which was washed
twice with 1 mL of acetone (0 °C) and dried: yield 112 mg (56%); mp
83 °C dec. Compound 4b was prepared analogously, using 3b (250 mg,
2) (a) Werner, H. J . Organomet. Chem. 1995, 500, 331-336. (b)
(
3) Werner, H.; Ortmann, D. A.; Gevert, O. Chem. Ber. 1996, 129,
3
0.30 mmol) and PiPr (64 µL, 0.33 mmol) as starting materials; dark
brown solid; yield 136 mg (61%); mp 65 °C dec.
4
11-417.
1
0.1021/om980984p CCC: $18.00 © 1999 American Chemical Society
Publication on Web 02/26/1999

Communications
Organometallics, Vol. 18, No. 6, 1999 953
Sch em e 2
4
a ,b at δ 234.7 (4a ) and 245.5 (4b) and thus at
significantly higher field than in the case of the rhodium
counterparts trans-[RhCl(dCR2)(PiPr3)2].1
,2b
The reactivity of the structurally related compounds
3
2
a and 4a toward NaC5H5 is quite different (see Scheme
). While the bis(phosphine) compound 4a is completely
inert toward NaC5H5 (THF, 25 °C), the mixed-ligand
derivative 3a reacts under the same conditions with
sodium cyclopentadienide to afford the half-sandwich-
8
type complex 5 in 70% isolated yield. In contrast to the
related methyleneiridium compound [C5Me5Ir(dCH2)-
(
PMe3)], generated by Klein and Bergman upon pho-
2
tolysis of the metallacycle [C5Me5Ir(κ -CH2CMe2O)-
(
F igu r e 1. ORTEP diagram of compound 5. Selected bond
distances (Å) and angles (deg): Ir-P 2.262(2), Ir-C1 1.904-
9
PMe3)] at -60 °C, the diphenylcarbene complex 5 is
exceptionally thermally stable and decomposes only at
temperatures above 93 °C. The X-ray crystal structure
analysis of 5 (Figure 1)10 reveals that the iridium has a
somewhat distorted trigonal coordination sphere if the
midpoint of the cyclopentadienyl ring is taken as one
coordination site. The metal-C(carbene) distance Ir-C
is almost identical to the Rh-C bond length (1.907(3)
Å) of the analogous carbenerhodium(I) complex [C5H5-
(
5), Ir-C14 2.308(7), Ir-C15 2.266(7), Ir-C16 2.210(7), Ir-
C17 2.239(7), Ir-C18 2.316(6), C1-C2 1.499(7), C1-C8
1
.492(7); P-Ir-C1 99.9(2), Ir-C1-C2 116.2(4), Ir-C1-
C8 134.5(4), C2-C1-C8 109.2(4).
Rh(CPh2)(CO)]11 but slightly longer than in the iridium
3
methylene derivative [Ir(dCH2){κ -N(SiMe2CH2PPh2)2}]
12
(
1.868(9) Å). To the best of our knowledge, compound
5
is the first structurally characterized cyclopentadi-
(
7) Selected spectroscopic data for 3a , 4a , and 5-9 (omitting the
1
1
3
1
enyliridium complex of the general composition [C5H5-
Ir(PR3)(L)], where L is a carbene, vinylidene, or alle-
nylidene ligand.
Treatment of 5 with dry HCl in pentane results in a
rapid change of color from violet to orange-yellow and
leads to the formation of the alkyl(chloro)iridium(III)
complex 6 (Scheme 3) in virtually quantitative yield.14
Diagnostic of an Ir-CHPh2 moiety in 6 is a resonance
H and C NMR data for the aryl groups) are as follows. 3a : H NMR
3
(
200 MHz, C
6
D
6
) δ 2.39 (m, 3 H, PCHCH
3
), 2.11 (sept, J (HH) ) 7.3
), 1.32 (d, J (HH) ) 7.3 Hz, 18 H, SbCHCH ), 1.19
3
dd, J (PH) ) 13.2, J (HH) ) 7.3 Hz, 18 H, PCHCH ); C NMR (50.3
2
3
13
Hz, 3 H, SbCHCH
3
3
3
3
13
(
1
6 6
MHz, C D ) δ 240.9 (d, J (PC) ) 7.6 Hz, IrdC), 24.8 (d, J (PC) ) 24.2
3
Hz, PCHCH
5.1 Hz, SbCHCH
NMR (400 MHz, C
3
), 22.0 (s, SbCHCH
3
), 20.0 (s, PCHCH
); P NMR (81.0 MHz, C ) δ 8.8 (s). 4a :
) δ 2.44 (m, 6 H, PCHCH ), 1.20 (dvt, N ) 13.2,
); C NMR (100.6 MHz, C ) δ 234.7
), 20.4 (s,
) δ 4.2 (s). 5: H NMR (200 MHz,
), 1.54 (m, 3 H, PCHCH ),
3
.98 (dd, J (PH) ) 13.1, J (HH) ) 6.9 Hz, 18 H, PCHCH ); C NMR
2
3
), 18.9 (d, J (PC)
3
1
1
)
3
6
D
6
H
6
D
6
3
3
13
J (HH) ) 7.0 Hz, 36 H, PCHCH
3
6 6
D
2
(
t, J (PC) ) 8.9 Hz, IrdC), 25.2 (vt, N ) 25.4 Hz, PCHCH
3
3
1
1
PCHCH
D
3
); P NMR (81.0 MHz, C
6
D
6
1
in the H NMR at δ 5.75 for the CH proton and a signal
in the C NMR spectrum at δ 24.9 for the substituted
methyl carbon atom. Due to P-H and P-C coupling,
3
C
0
(
6
6
) δ 4.92 (d, J (PH) ) 1.1 Hz, 5 H, C
5
H
5
3
1
3
3
3
13
2
50.3 MHz, C
3.8 Hz, C
P NMR (81.0 MHz, C
δ 5.75 (d, J (PH) ) 2.2 Hz, 1 H, CH(C
H, C
.1 Hz, 12 H, PCHCH
H, PCHCH
6
H
D
6
) δ 217.2 (d, J (PC) ) 12.7 Hz, IrdC), 82.3 (d, J (PC)
1
)
5
5
), 28.0 (d, J (PC) ) 28.0 Hz, PCHCH
3
), 20.8 (s, PCHCH
) δ 27.8 (s). 6: H NMR (200 MHz, CD Cl
), 5.09 (d, J (PH) ) 1.5 Hz,
3
);
3
1
1
6
D
6
2
2
)
3
3
6
H
5
)
2
(10) Crystal data for 5: crystals from pentane; crystal size 0.22 ×
3
3
5
7
5
H
5
), 2.44 (m, 3 H, PCHCH
3
), 1.20 (dd, J (PH) ) 14.4, J (HH) )
0.16 × 0.13 mm; monoclinic, space group P2
1
/n (No. 14), Z ) 4; a )
3
3
3
), 0.81 (dd, J (PH) ) 12.6, J (HH) ) 7.1 Hz, 6
11.017(2) Å, b ) 14.709(2) Å, c ) 15.374(3) Å, â ) 96.01(1)°, V ) 2477.7-
3 -3
1
3
2
3
); C NMR (50.3 MHz, C
6
D
6
) δ 83.4 (d, J (PC) ) 2.8 Hz,
(7) Å , dcalcd ) 1.565 g cm ; 2θ(max) ) 49.90° (Mo-KR, λ ) 0.710 73
Å, graphite monochromator, ω/θ scan, Zr filter with factor 15.4, T )
293(2) K.; 4496 reflections scanned, 4328 unique, 3565 observed (I >
2σ(I)), Lorentz-polarization and empirical absorption corrections (ψ
scans, minimum transmission 83.92%); direct methods (SHELXS-86),
2
1
C H ), 24.9 (d, J (PC) ) 6.5 Hz, CHPh ), 23.5 (d, J (PC) ) 27.8 Hz,
5
5
2
31
PCHCH
.5 (s). 7: H NMR (200 MHz, C
CHPh ), 4.93 (m, 2 H, C ), 4.49, 4.31 (both m, 1 H each, C
m, 3 H, PCHCH ), 0.96 (dd, J (PH) ) 13.9, J (HH) ) 7.3 Hz, 18 H,
PCHCH ), -14.40 (d, J (PH) ) 33.4 Hz, 1 H, IrH); C NMR (50.3 MHz,
) δ 121.8 (d, J (PC) ) 4.6 Hz, CCHPh
J (PC) ) 9.2 Hz, C ), 74.8, 67.6 (both s, C
d, J (PC) ) 31.4 Hz, PCHCH ), 19.8, 19.5 (je s, PCHCH
3
), 20.8, 19.1 (both s, PCHCH
3
); P NMR (81.0 MHz, C
6
D
6
) δ
) δ 5.70 (d, J (PH) ) 2.2 Hz, 1 H,
), 2.13
1
3
5
6 6
D
2
5
H
4
5 4
H
3
3
(
3
269 parameters, reflex/parameter ratio 16.08; R1 ) 0.0287, wR2 )
2
13
-3
3
0.0696; residual electron density +0.697/-0.568 e Å .
2
C
6
D
6
2
), 84.0 (s, C
5
H
4
), 77.1 (d,
), 26.6
(11) Mahr, N. Dissertation, Universit a¨ t W u¨ rzburg, 1994.
(12) Fryzuk, M. D.; MacNeil, P. A.; Rettig, S. J . J . Am. Chem. Soc.
1985, 107, 6708-6710.
2
5
H
4
5
H
4
), 47.9 (s, CHPh
2
1
31
(
(
3
3
); P NMR
) δ 2.61 (m, 6
3
), 1.27, 1.19 (both dvt, N ) 14.6, J (HH) ) 7.3 Hz, 18 H
1
81.0 MHz, C
H, PCHCH
each, PCHCH
6
D
6
) δ 37.5 (s). 8: H NMR (200 MHz, C
6
D
6
(13) (a) D o¨ tz, K. H.; Fischer, H.; Hofmann, P.; Kreissl, F. R.;
Schubert, U.; Weiss, K. Transition Metal Carbene Complexes; Verlag
Chemie: Weinheim, 1983. (b) Bruce, M. I. Chem. Rev. 1991, 91, 197-
257.
3
3
1
3
), -19.23 (br s, 1 H, IrH); P NMR (81.0 MHz, C
6
D
6
) δ
3
1
1
1
.65 (s). 9: H NMR (200 MHz, CD
2
Cl
2
) δ 2.30 (m, 6 H, PCHCH
),
),
3
.11, 1.03 (both dvt, N ) 14.5, J (HH) ) 7.3 Hz, 18 H each, PCHCH
3
(14) The preparation of 6 is as follows. A slow stream of dry HCl
was passed through a solution of 5 (69 mg, 0.12 mmol) in 5 mL of
pentane at room temperature. After a few minutes, a change of color
from violet to orange-yellow occurred and an orange-yellow solid
precipitated. After the solution was stirred at -30 °C for 2 h, the solid
was separated from the mother liquor, washed with 1 mL of pentane
(0 °C), and dried: yield 71 mg (97%), mp 60 °C dec. For the
isomerization from 6 to 7, a solution of 6 (120 mg, 0.19 mmol) in 10
mL of benzene was refluxed for 2 min. After the solution was cooled
to room temperature, the solvent was removed and the oily residue
2
13
-
28.8 (t, J (PH) ) 11.6 Hz, 1 H, IrH); C NMR (50.3 MHz, CD
2
Cl
2
) δ
3
2
66.5 (s, IrdC), 24.9 (vt, N ) 28.0 Hz, PCHCH
3
), 19.7 (s, PCHCH
);
3
1
P NMR (81.0 MHz, CD
8) The preparation of 5 is as follows. A solution of 3a (138 mg, 0.19
mmol) in 25 mL of THF was treated with small portions of NaC
85 mg, 0.97 mmol) and stirred for 1 h at room temperature. After the
2 2
Cl ) δ 38.2 (s).
(
5
H
5
(
solvent was removed in vacuo, the residue was suspended in 20 mL of
pentane and the solution was filtered. The filtrate was brought to
dryness in vacuo, and the oily residue was recrystallized from pentane
(
2 mL) at -78 °C. Dark violet crystals were obtained, which were
2 2
dissolved in 1 mL of CH Cl . Upon addition of 10 mL of hexane and
separated from the mother liquor, washed with small quantities of
pentane (0 °C), and dried: yield 77 mg (70%); mp 93 °C dec.
careful concentration of the solution in vacuo, pale yellow air-sensitive
crystals were obtained. They were separated from the mother liquor,
washed with 1 mL of pentane (-20 °C), and dried: yield 114 mg (95%),
mp 106 °C dec.
(9) Klein, D. P.; Bergman, R. G. J . Am. Chem. Soc. 1989, 111, 3079-
3
080.

9
54 Organometallics, Vol. 18, No. 6, 1999
Communications
Sch em e 3
is formed, the elemental analysis reveals that in the
solid state an unsolvated species is present. The 1
H
NMR spectrum of 9 displays a high-field signal (triplet)
at δ -28.8 for the hydrido ligand, while the 13C NMR
spectrum exhibits a low-field resonance at 266.5 for the
7
carbene carbon atom. The appearance of this carbon
signal at significantly lower field compared to 4a (δ
Sch em e 4
234.7) and the methyleneiridium complex [Ir(dCH2)-
3
{
κ -N(SiMe2CH2PPh2)2}] (δ 200.1) could be due at least
partly to the fact that the complex is cationic. Since
according to the spectroscopic data the two phenyl
groups are inequivalent, we tentatively propose a
square-pyramidal geometry for the five-coordinate cat-
ion of 9 with the carbene ligand in the apical position.
The free coordination site of 9 is readily occupied by
chloride, and thus upon addition of NaCl to a solution
of 9 in benzene/water the neutral species 8 is formed.
In this context we note that most recently Kaska,
Mayer, and co-workers discussed the generation of a
labile, five-coordinate carbene(carbonyl)hydridoiridium
species in which, however, the metal is in the +I and
1
8
not, like in 9, in the +III oxidation state.
both of these signals are split into doublets.7 Upon
warming a solution of 6 in benzene for 2 min to reflux
temperature, an isomerization occurs and the chloro-
In conclusion, we have shown that by choosing the
mixed-ligand system 2 as the starting material the
preparation of a variety of new carbeneiridium com-
plexes with different structural features can be achieved.
The square-planar representative 4a , containing a metal
center with a 16-electron configuration, and the half-
sandwich-type compound 5, containing a metal center
with an 18-electron configuration, behave differently
toward acids HX, the former yielding a product with
IrH(dCPh2) and the latter with Ir-CHPh2 as a molec-
ular unit. We are currently exploring the scope and
mechanism of C-C coupling reactions of the diarylcar-
beneiridium complexes, particularly with olefins as
substrates.
(
hydrido)iridium derivative 7 is formed.14 We assume
that the initial step of the conversion of 6 to 7 consists
of the migration of the CHPh2 unit from the metal
center to the five-membered C5H5 ring forming an
4
intermediate with a η -coordinated C5H5CHPh2 cyclo-
pentadiene ligand. We note that if the isomerization
process of 6 to 7 is followed (in C6D6) by 1H NMR
spectroscopy, the formation of a new compound can be
observed for which the appearance of two doublets at δ
3
.42 and 3.19 (with a H-H coupling of ca. 10 Hz) is
1
5
characteristic. In agreement with earlier observations,
we conclude that these signals belong to the four-
4
coordinate iridium(I) species [IrCl(η -C5H5CHPh2)-
Ack n ow led gm en t. We gratefully acknowledge fi-
nancial support from the Deutsche Forschungsgemein-
schaft (Grant No. SFB 347), the Fonds der Chemischen
Industrie, and BASF AG.
(PiPr3)], which subsequently rearranges via a 1,2-
hydrogen shift from the ring to iridium to give 7. The
1
H NMR spectrum of 7 exhibits a resonance for the
hydrido ligand at δ -14.4, which is shifted by ca. 2.2
ppm to higher field compared with the rhodium com-
5
15
pound [(η -C5H4CHPh2)RhHCl(PiPr3)].
Su p p or tin g In for m a tion Ava ila ble: A table with the
elemental analyses of compounds 2, 3a , 3b, 4a , 4b, 5, 6, 7,
and 9 as well as fully labeled diagrams and tables of crystal-
lographic data, data collection, solution and refinement details,
positional and thermal parameters, and both distances and
angles for 5. This material is available free of charge via the
Internet at http://pubs.acs.org.
We have also examined the reactivity of the square-
planar carbeneiridium(I) complex 4a toward acids HX.
Upon exposure of a solution of 4a in benzene to dry HCl,
a deep green compound is formed which is very labile
and could not be isolated in analytically pure state. On
1
the basis of its H NMR spectrum, the reaction product
OM980984P
from 4a and HCl is the dichlorohydridoiridium(III)
complex 8 (Scheme 4), which is generated via oxidative
addition of the electrophile to the electron-rich metal
center. The most typical spectroscopic feature of 8 is the
hydride resonance at δ -19.2 which appears in the same
region as that of related octahedral hydridobis(triiso-
(
16) (a) Werner, H.; H o¨ hn, A. Z. Naturforsch., B 1984, 39, 1505-
509. (b) H o¨ hn, A.; Werner, H. J . Organomet. Chem. 1990, 382, 255-
1
2
72.
(17) The preparation of 9 is as follows. A solution of 4a (61 mg, 0.09
mmol) in 10 mL of CH
2
Cl
2
/pentane (1:1) was treated dropwise with
as long as the formation of a red
precipitate occurred. After 5 mL of distilled water was added to the
solution, the liquid phase was removed and the residue extracted with
an aqueous solution (50%) of HBF
4
1
6
propylphosphine) iridium derivatives.
In contrast to compound 8, the product obtained upon
treatment of 4a with aqueous HBF4 is quite stable and
has been characterized by elemental analysis and
spectroscopic techniques.17 The red air-sensitive solid
1
2 2
0 mL of CH Cl . The extract was concentrated to ca. 5 mL in vacuo
and then layered with pentane. Upon storing for 2 h, the almost
colorless mother liquor was separated, and the remaining red solid
was washed with 5 mL of pentane and dried: yield 65 mg (95%); mp
1 °C dec.
18) (a) Nemeh, S.; Flesher, R. J .; Gierling, K.; Maichle-M o¨ ssmer,
C.; Mayer, H. A.; Kaska, W. C. Organometallics 1998, 17, 2003-2008.
(b) Alias, F. M.; Poveda, M. L.; Sellin, M.; Carmona, E.; Gutierrez-
Puebla, E.; Monge, A. Organometallics 1998, 17, 4124-4126. (c) Alias,
F. M.; Poveda, M. L.; Sellin, M.; Carmona, E. J . Am. Chem. Soc. 1998,
120, 5816-5817. (d) Luecke, H. F., Bergman, R. G. J . Am. Chem. Soc.
1998, 120, 11008-11009.
9
9
is soluble in acetone and CH2Cl2 (but insoluble in
(
benzene and ether) and can be stored under argon for
days. While it is conceivable that in acetone a 1:1 adduct
(15) Herber, U.; Bleuel, E.; Gevert, O.; Laubender, M.; Werner H.
Organometallics 1998, 17, 10-12.