Metal-dependent stabilization of Si-S bonds to hydrolysis in iridium and rhodium silyls. Hydrolyzability as a probe for Si-H reductive elimination

Article abstract of DOI:10.1021/om950791r

The iridium (triethylthio) silyl complexes cis(PPh₃)₂(CO)IrH₂(Si(SEt)₃) (5), fac-(PMe₃)₃Ir(CH₃(H)-(Si(SEt)₃) (6), and mer-(PMe₃)₃Ir(C₆F₅)(H)(Si(SEt) ₃) (7) were synthesized by oxidative addition of HSi(SEt)₃ (1) to HIr(CO)(PPh₃)₃ (2), CH₃Ir(PMe₃)₄ (3), and C₆F₅-Ir(PMe₃)₃ (4), respectively. 4 was synthesized by the reaction between Ir(PMe₃)₄Cl and C₆F₅MgBr. The rhodium analog of 7, mer-(PMe₃)₃Rh(C₆F₅)(H)(Si(SEt) ₃) (9), was obtained similarly from C₆F₅Rh(PMe₃)₃, (8) and 1. Unlike the extremely easily hydrolyzable parent silane 1, compounds 5-7 are stable in H₂O/THF and even in NaOH/H₂O/THF solutions. This stabilization is attributed to the electron-donating capacity of the Ir centers, which efficiently reduces electrophilicity of the silicon. Reactivity of the rhodium complex 9 is strikingly different, cleanly producing in the presence of 5 equiv of H₂O the ethylthio-complex mer-(PMe₃)₃Rh(C₆F₅)(H)(SEt) (10). Compound 10 was identified spectroscopically and was synthesized independently from 8 and HSEt. A plausible scheme accounting for the generation of 10 under the hydrolysis conditions is presented. The observed difference in the reactivities of 5-7 and 9 is explained in terms of their different tendencies to reductively eliminate H-Si(SEt)₃.

Full text of DOI:10.1021/om950791r

Organometallics 1996, 15, 1075-1078
1075
Meta l-Dep en d en t Sta biliza tion of Si-S Bon d s to
Hyd r olysis in Ir id iu m a n d Rh od iu m Silyls.
Hyd r olyza bility a s a P r obe for Si-H Red u ctive
Elim in a tion
Michael Aizenberg, Roman Goikhman, and David Milstein*
Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
Received October 5, 1995X
Summary: The iridium (triethylthio)silyl complexes cis-
(PPh3)2(CO)IrH2(Si(SEt)3) (5), fac-(PMe3)3Ir(CH3)(H)-
(Si(SEt)3) (6), and mer-(PMe3)3Ir(C6F5)(H)(Si(SEt)3)
(7) were synthesized by oxidative addition of HSi(SEt)3
(1) to HIr(CO)(PPh3)3 (2), CH3Ir(PMe3)4 (3), and C6F5-
Ir(PMe3)3 (4), respectively. 4 was synthesized by the
reaction between Ir(PMe3)4Cl and C6F5MgBr. The rhod-
ium analog of 7, mer-(PMe3)3Rh(C6F5)(H)(Si(SEt)3) (9),
was obtained similarly from C6F5Rh(PMe3)3, (8) and 1.
Unlike the extremely easily hydrolyzable parent silane
1, compounds 5-7 are stable in H2O/ THF and even in
NaOH/ H2O/ THF solutions. This stabilization is at-
tributed to the electron-donating capacity of the Ir
centers, which efficiently reduces electrophilicity of the
silicon. Reactivity of the rhodium complex 9 is strikingly
different, cleanly producing in the presence of 5 equiv of
H2O the ethylthio-complex mer-(PMe3)3Rh(C6F5)(H)(SEt)
(10). Compound 10 was identified spectroscopically and
to examine the reactivity of derivatives of much more
easily hydrolyzable silane, namely HSi(SEt)3. In the
present paper we report that coordination to Ir(III)
centers causes remarkable stabilization of an (alkyl-
thio)silyl group to hydrolysis. Moreover, this group
becomes stable even to alkaline conditions. In striking
difference, an exactly analogous Rh(III) complex under-
goes facile hydrolysis. We show that this is a result of
the reactivity of free HSi(SEt)3. This hydrolyzability of
thiosilyl ligands provides a simple tool to detect whether
or not Si-H reductive elimination is operative, even
when its formation equilibrium lies far to the left.
Resu lts a n d Discu ssion
4
Addition of the silane HSi(SEt)3 (1) to benzene
5a
6a
solutions of HIr(CO)(PPh3)3 (2), CH3Ir(PMe3)4 (3),
and C6F5Ir(PMe3)3 (4) at room temperature yields the
oxidative addition products 5-7, respectively. The
composition and stereochemistry of the complexes un-
equivocally follow from their NMR data and from their
comparison with those of known fully characterized
analogs.5b,6b,7
was synthesized independently from 8 and HSEt.
A
plausible scheme accounting for the generation of 10
under the hydrolysis conditions is presented. The ob-
served difference in the reactivities of 5-7 and 9 is
explained in terms of their different tendencies to reduc-
tively eliminate H-Si(SEt)3.
In tr od u ction
Complexes that contain a metallo-silanol fragment,
M-Si-OH, have been an object of considerable recent
interest.1-3 They were reported to be accessible from
hydrolysis of Fe, Os, and Pt silyl complexes,1 from oxy-
functionalization of M-Si-H compounds (M ) Fe, W)
by use of dimethyldioxirane,1c,2 and from direct Si-H
oxidative addition of secondary silanols to a low-valent
electron-rich iridium(I) center.3
In the course of our studies of the approaches to
synthesis of metallo-silanols and their derivatives, we
tested several IrIII-Si-X systems with regard to their
succeptibility to selective hydrolysis of Si-X bonds.
Preliminary experiments indicated that, in contrast to
reported Os(II)1b and Fe(II)2 chlorosilyls, triethoxysilyl
complexes of Ir(III), such as mer-(PEt3)3Ir(Cl)(H)(Si-
(OEt)3) (12) and trans-(PEt3)2Ir(H)(Cl)(Si(OEt)3) (13),
cannot be hydrolyzed selectively. Under mild conditions
they are hydrolytically stable, while forcing conditions
lead to cleavage of the metal-silicon bonds. This led us
Complex 5 exhibits in the 31P{1H} NMR spectrum two
mutually coupled doublets of equal intensity, indicating
(4) (a) Wolinski, L.; Tieckelmann, H.; Post, H. W. J . Org. Chem.
1951, 16, 395. (b) Lambert, J . B.; Shulz, W. J ., J r.; McConnell, J . A.;
Schilf, W. J . Am. Chem. Soc. 1988, 110, 2201.
(5) (a) Wilkinson, G. Inorg. Synth. 1972, 13, 126. (b) Reactions of 2
with other silanes were studied previously, and the fully characterized
products exhibited 1H NMR data completely analogous to those
reported herein for 5; see: Harrod, J . F.; Gilson, D. F. R.; Charles, R.
Can. J . Chem. 1969, 47, 2205.
X Abstract published in Advance ACS Abstracts, J anuary 15, 1996.
(1) (a) Chang, L. S.; J ohnson, M. P.; Fink, M. J . Organometallics
1991, 10, 1219. (b) Rickard, C. E. F.; Roper, W. R.; Salter, D. M.;
Wright, L. J . J . Am. Chem. Soc. 1992, 114, 9682. (c) Malisch, W.;
Schmitzer, S.; Kaupp, G.; Hindahl, K.; Ka¨b, H.; Wachtler, U. In
Organosilicon Chemistry. From Molecules to Materials; Auner, N.,
Weis, J ., Eds.; VCH: Weinheim, Germany, 1994; p 185.
(2) Adam, W.; Azzena, U.; Prechtl, F.; Hindahl. K.; Malisch, W.
Chem. Ber. 1992, 125, 1409.
(6) (a) Thorn, D. L. Organometallics 1982, 1, 197. (b) Ph3Si, (EtO)3Si,
and Et3Si analogs of 6 are fully characterized and exhibit completely
analogous spectral data; see: Thorn, D. L.; Harlow, R. L. Inorg. Chem.
1990, 29, 2017. Aizenberg, M.; Milstein, D. Angew. Chem. 1994, 106,
344; Angew. Chem., Int. Ed. Engl. 1994, 33, 317. Aizenberg, M.;
Milstein, D. J . Am. Chem. Soc. 1995, 117, 6456.
(7) An analog of complexes 7 and 9, namely mer-(PMe3)3Rh(C6F5)-
(H)(Si(OEt)3) (11), which was prepared similarly and was fully
characterized, exhibited spectral data analogous to those reported
herein for 7 and 9; see: Aizenberg, M.; Milstein, D. Science 1994, 265,
359.
(3) Goikhman, R.; Aizenberg, M.; Kraatz, H.-B.; Milstein, D. J . Am.
Chem. Soc. 1995, 117, 5865.
0276-7333/96/2315-1075$12.00/0 © 1996 American Chemical Society

1076 Organometallics, Vol. 15, No. 3, 1996
Notes
Sch em e 1. F or m a tion of th e Rh od iu m Com p lexes
a cis-phosphine configuration. The signal at δ 1.9 ppm
2
has characteristic 29Si satellites with J P-Si,trans ) 157
9-11
Hz.8 1H NMR clearly indicates the presence of two
different hydrides whose signals are coupled to each
other and are also split by two different phosphorus
nuclei. The hydride signal at δ -10.21 ppm has a
typical, large 2J H-P,trans value of 104.3 Hz. The carbonyl
carbon gives rise to a doublet of doublets in the 13C-
{1H} NMR spectrum at δ 179.8 ppm with two different
2J C-P,cis couplings of 7.4 and 4.2 Hz.
PMe3
PMe3
C6F5
H
HSi(SEt)3
C6F5
Rh PMe3
Rh
PMe3
Si(SEt)3
PMe3
PMe3
9
8
H2O
+HSi(OEt)3,
–HSi(SEt)3
HSEt
The facial configuration of complex 6 clearly follows
from the presence of three mutually coupled signals in
its 31P{1H} NMR spectrum. Its 1H NMR spectrum
contains appropriately split signals due to the iridium-
bound methyl group at δ 0.51 ppm and due to the
hydride at δ -12.35 ppm; the protons of the PMe3
ligands give rise to three doublets.
PMe3
PMe3
C6F5
C6F5
H
H
Rh
Rh
PMe3
SEt
PMe3
Si(OEt)3
PMe3
PMe3
10
11
Complex 7 exhibits in the 31P{1H} NMR spectrum two
signals integrated as 2:1, the signal of the unique
phosphine appearing as a doublet of doublets of triplets
Sch em e 2. Rea ctivity of 9 in th e P r esen ce of H2O
PMe3
C6F5
H
C6F5Rh(PMe3)3 + HSi(SEt)3
Rh
4
1
due to additional J P-F couplings. The H NMR spec-
trum of 7 contains a signal of a hydride at δ -12.0 ppm
which is also additionally split by one of the aromatic
fluorines. The protons of the mutually trans PMe3
ligands give rise to a virtual triplet, indicative of the
meridional configuration. The presence of the C6F5
group is expressed in the 19F{1H} NMR spectrum as five
multiplets of equal intensity. Two of them, which are
due to ortho fluorines, are significantly shifted to lower
field and appear at δ -95.5 and -102.4 ppm.9
PMe3
Si(SEt)3
8
1
PMe3
9
H2O
HSi(SEt)3
HSEt + [HSiO1.5 n
]
PMe3
C6F5
H
C6F5Rh(PMe3)3 + HSEt
Rh
PMe3
SEt
8
PMe3
10
The 1H NMR spectra of complexes 5-7 contain
signals of appropriate intensity and multiplicity due to
Si(SCH2CH3)3 groups bound to the iridium centers.
Attempted hydrolysis of 5-7 did not result in the
formation of silanol complexes. No reaction was ob-
served with a 280-fold excess of H2O in THF after 1 day.
Moreover, even 3 equiv of NaOH in THF/H2O solution
did not affect the complexes after 10 h.10 Similarly, the
triethoxysilyl Ir(III) complexes 12 and 13, obtained by
oxidative addition of HSi(OEt)3 to Ir(PEt3)3Cl and Ir-
(PEt3)2(C2H4)Cl, respectively, are also stable at room
temperature in the presence of an excess of H2O in
dioxane and can be recovered easily.
To test whether the nature of the metal center alone
can influence the capability of the MSi(SEt)3 fragment
to hydrolyze, we prepared the exact analog of 7, namely
mer-(C6F5)(H)(Si(SEt)3)Rh(PMe3)3 (9),11 and examined
its reactivity. This complex is readily accessible7 from
the reaction of (C6F5)Rh(PMe3)3 (8) with 1 (Scheme 1).
The main features of the NMR spectra of complex 9 are
the same as those of 7.
reaction was the ethylthio complex 10, rather than the
expected metallo-silanol.
The 31P{1H} NMR spectrum of 10 exhibits two signals
1
in a 1:2 ratio. The small value J P-Rh ) 98.2 Hz,
observed for the mutually trans phosphines, is indica-
tive of a Rh(III) complex. The signal due to the unique
PMe3 appears as a multiplet, undoubtedly because of
additional couplings to the fluorines of the C6F5 group.
The 1H NMR spectrum contains a high-field hydride
signal with a large H-trans-to-P coupling constant and
(as in the cases of 7 and 9) virtual triplet and doublet
patterns for the protons of the PMe3 ligands. Impor-
tantly, the signals of the SCH2CH3 group, which appear
as a regular quartet and triplet (3J H-H ) 7.6 Hz), are
integrated as two and three protons, leaving no doubt
about the presence of only one such group in the
complex. The 19F{1H} NMR spectrum consists, again,
of five different signals, two of which are significantly
deshielded.12 The identity of 10 was also confirmed by
its independent synthesis from 8 and EtSH13 (Scheme
1).
Quite unexpectedly, 9 was completely consumed
already after 3 h at room temperature in the presence
of 5 equiv of H2O in C6D6. At the same time,formation
of a white precipitate (probably silica) was observed.
However, the only organometallic product formed in the
There are two important observations that require
further explanation. The first is the striking difference
in the reactivities of HSi(SEt)3 and IrIII-Si(SEt)3 toward
O-nucleophiles. The second is the major influence of
(8) Ozawa, F.; Hikida, T.; Hayashi, T. J . Am. Chem. Soc. 1994, 116,
2844.
(9) (a) Bruce, M. I. J . Chem. Soc. A 1968, 1459. (b) Bennett, R. L.;
Bruce, M. I.; Gardner, R. C. F. J . Chem. Soc. Dalton Trans. 1973, 2653.
(10) We also checked reactivity of complex 7 toward water under
(12) Restricted rotation of a pentafluorophenyl group, which gives
rise to five instead of the usual three signals in 19F NMR, is known.
See, for example: (a) Bennett, R. L.; Bruce, M. I.; Goodfellow. R. J . J .
Fluorine Chem. 1972/73, 2, 447. (b) Reference 9b.
acidic conditions. 7 slowly decomposes in
presence of 3 equiv of CF3COOH and 100 equiv of H2O at room
a
THF solution in the
(13) For RS-H oxidative additions see, for example: (a) Singer, H.;
Wilkinson, G. J . Chem. Soc. A 1968, 2516. (b) Crooks, G. R.; J ohnson,
B. F. G.; Lewis, J .; Williams, I. G. J . Chem. Soc. A 1969, 797. (c)
Stiddard, M. H. B.; Townsend, R. E. J . Chem. Soc. A 1970, 2719. (d)
Rauchfuss, T. B.; Roundhill, D. M. J . Am. Chem. Soc. 1975, 97, 3386.
(e) Collman, J . P.; Rothrock, R. K.; Stark, R. A. Inorg. Chem. 1977,
16, 437.
temperature to
a mixture of uncharacterized products, a major
compound still remaining (42%, as judged by 31P{1H} NMR) after 2
days.
(11) Attempts to prepare rhodium analogs of 5 and 6 were unsuc-
cessful.

Notes
Organometallics, Vol. 15, No. 3, 1996 1077
the nature of the metal center on the hydrolytic behavior
of the completely analogous complexes 7 and 9.
reductively eliminates 1, while 5 does not,17 as evi-
denced by its stability in the presence of H2O.
Mechanistically, the hydrolysis of the Si-SEt bond
proceeds by nucleophilic attack of OH- or H2O at the
Si center. The resulting species which would then
contain Si-OH bonds are expected to be thermodynami-
cally more stable than the precursor thiosilyl species.
The fact that all the IrIII-Si(SEt)3 complexes studied
are stable for hours in NaOH/H2O/THF medium, while
free HSi(SEt)3 hydrolyzes instantaneously even in the
presence of traces of water, can be explained by the
electronic influence of the Ir center. Its strong electron-
donating capacity efficiently reduces the electrophilicity
of the Si(SEt)3 fragment and hence its succeptibility
to nucleophilic attack. Steric factors may also play a
role. It is noteworthy that a related phenomenon was
observed for platinum(IV)-tin complexes, such as
PtMe2Cl(bpy)(SnRnCl3-n) (R ) Ph, Me; n ) 1, 2). No
reaction between these complexes and water or other
Lewis bases took place, and the starting compounds
could be recovered at low temperatures.14
Regarding the hydrolytic reactivity of the rhodium
complex 9, we propose that complex 10 is a result of
EtS-H oxidative addition to 8. Complex 8 and EtSH
are, in turn, available as products of reductive elimina-
tion of H-Si(SEt)3 from 9 and of the hydrolysis of free
1, respectively (Scheme 2). This hypothesis was verified
not only by preparation of 10 from 8 and EtSH (see
above) but also by silane exchange experiments. When
HSi(OEt)3 (10 equiv) was added to a C6D6 solution of
complex 9 at room temperature, 80% conversion to the
known mer-(C6F5)(H)(Si(OEt)3)Rh(PMe3)3 (11)7 and free
HSi(SEt)3 was observed by NMR after two days, thus
establishing the equilibrium 9 h 8 + 1 (Scheme 2). It
is noteworthy that this equilibrium lies far to the left,
the equilibrium concentration of the undetected free 1
being very low. It is sufficient, however, for HSi(SEt)3
to be efficiently removed by the irreversible hydrolysis.
Importantly, under the same conditions neither 5 nor
7 undergoes such Si(SEt)3/Si(OEt)3 exchange, remaining
unchanged at room temperature after 2 days as detected
by NMR.
Con clu sion s
The results presented here clearly demonstrate that
(i) ligation to a late transition metal significantly
reduces the succeptibility of an (alkylthio)silyl group to
nucleophilic attack, making it hydrolytically stable, (ii)
even completely analogous complexes of the second- and
third-row transition metals, e.g. Rh and Ir, can exhibit
strikingly different hydrolytic reactivities due to their
different propensities for reductive elimination, (iii) use
of extremely easily hydrolyzable silanes, such as HSi-
(SEt)3, makes possible an indirect but efficient detection
of Si-H reductive elimination.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All the manipulations of air-
and moisture-sensitive compounds were carried out using a
nitrogen-filled Vacuum Atmospheres glovebox. The solvents
used were purified by standard procedures, degassed, and
stored over molecular sieves in the glovebox. All the reagents
were of reagent grade. HSi(SEt)3,4 HIr(CO)(PPh3)3,5a CH3Ir-
(PMe3)4,6a C6F5Rh(PMe3)3,7 Ir(PMe3)4Cl,18 Ir(PEt3)3Cl,19 and Ir-
(PEt3)2(C2H4)Cl3 were prepared according to the literature
procedures. NMR spectra were obtained with a Bruker AMX
400 spectrometer at ambient probe temperature in C6D6 (99%
D, Riedel-de Hae¨n) solutions unless otherwise specified.
Chemical shifts are reported in ppm and are referenced to
internal residual C6D5H at δ 7.15 (1H NMR, 400 MHz),
external 85% H3PO4 in D2O at δ 0.0 (31P NMR, 162 MHz),
internal C6D6 at δ 128.00 (13C NMR, 100 MHz), and external
C6F6 at δ -162.9 (19F NMR, 376 MHz). Abbreviations are as
follows: d, doublet; t, triplet; q, quartet; m, multiplet; v,
virtual; br, broad; app, apparent. IR spectra were recorded
with a Nicolet 510 FT-IR spectrometer using NaCl plates.
Elemental analyses were obtained from the Microanalysis
Laboratory of The Hebrew University of J erusalem.
P r ep a r a tion of (C6F 5)Ir (P Me3)3 (4). To a suspension of
100 mg (0.188 mmol) of Ir(PMe3)4Cl in 7 mL of THF was
dropwise added 2.1 mL of a 0.10 M solution of C6F5MgBr in
THF/Et2O (4:1) (1.12 equiv). After the addition was complete
(ca. 20 min), the mixture was stirred for 10 min more and then
the solvent was removed under vacuum. The residue was
extracted with pentane (3 × 3 mL); the extract after filtration
was evacuated to yield 71 mg (64%) of 4 as orange needles.
Anal. Calcd for C15H27F5IrP3: C, 30.67; H, 4.63. Found: C,
30.95; H, 4.48. 31P{1H} NMR (C6D6): δ -34.4 (m, 1P), -27.2
(d, J ) 25.4 Hz, 2P). 1H NMR (C6D6): δ 0.95 (vt, J ) 3.0 Hz,
18H, CH3-P), 1.16 (d, J ) 7.1 Hz, 9H, CH3-P). 19F{1H} NMR
(C6D6): δ -111.5 (m, 2F, ortho), -163.2 (m, 1F, para), -163.7
(m, 2F, meta).
We believe that the observed difference in reactivity
between the Rh complex 9 and the Ir complexes 5-7
originates from their different tendencies to reductively
eliminate the Si-H bond,15 rather than to hydrolyze.
Although we are unaware of a direct comparison of
Si-H reductive elimination from isostructural Ir(III)
and Rh(III) complexes, trimethylphosphine Rh(III) com-
plexes have a much higher propensity to undergo C-H
reductive elimination than the analogous Ir(III) com-
plexes,16 as expected for a comparison between second-
and third-row metals. However, it is worth noting that
although the electron density at the Rh center in the
PMe3 complex 9 is definitely lower than that at the Ir
centers in the PMe3 complexes 6 and 7, it may be
comparable to that of the Ph3P complex 5. Still, 9
P r ep a r a tion of cis-(P P h 3)2(CO)Ir H2(Si(SEt)3) (5). To a
solution of 30 mg (0.03 mmol) of HIr(CO)(PPh3)3 in 1 mL of
C6D6 was added 6 µL (6.3 mg, 0.03 mmol) of HSi(SEt)3. The
initial greenish color of the reaction mixture slowly disap-
peared during 15 min. NMR analysis of the resulting colorless
solution indicated quantitative formation of 5 and liberation
of 1 equiv of PPh3. The solvent was removed under vacuum
to yield 36 mg of the 1:1 mixture of 5 and PPh3. Anal. Calcd
for C61H62IrOP3S3Si (C43H47IrOP2S3Si + 1 (C6H5)3P): C, 60.03;
(14) Kuyper, J . Inorg. Chem. 1977, 16, 2171.
(15) The reductive elimination of Si-H bonds is well-known, and
its kinetics was investigated. See for example: (a) Haszeldine, R. N.;
Parish, R. V.; Taylor, R. J . J . Chem. Soc., Dalton Trans. 1974, 2311.
(b) Hostetler, M. J .; Bergman, R. G. J . Am. Chem. Soc. 1990, 112, 8621.
(c) Hostetler, M. J .; Butts, M. D.; Bergman, R. G. Organometallics 1993,
12, 65. (d) J ohnson, C. E.; Eisenberg, R. J . Am. Chem. Soc. 1985, 107,
6531. (e) Hays, M. K.; Eisenberg, R. Inorg. Chem. 1991, 30, 2623. (f)
Cleary, B. P.; Mehta, R.; Eisenberg, R. Organometallics 1995, 14, 2297
and references therein.
(17) The Si(OEt)3 analog of 5 was reported to be extremely stable
with regard to loss of HSi(OEt)3. The Ir-D/H-Si(OEt)3 exchange
reactions of its monodeuterido isotopomer were, therefore, proposed
to proceed by concerted bimolecular mechanism, rather than by a
reductive elimination-oxidative addition sequence.5b
(18) Herskovitz, T. Inorg. Synth. 1982, 21, 99.
(19) Casalnuovo, A. L.; Calabrese, J . C.; Milstein, D. J . Am. Chem.
Soc. 1988, 110, 6738.
(16) See, for example: Milstein, D. Acc. Chem. Res. 1984, 17, 221.

1078 Organometallics, Vol. 15, No. 3, 1996
Notes
H, 5.12. Found: C, 60.00; H, 5.14. 31P{1H} NMR (C6D6): δ
1.9 (d, J ) 13.8 Hz, 1P), 5.4 (d, J ) 13.8 Hz, 1P), -4.8 (s, 1P,
free PPh3). 1H NMR (C6D6): δ -10.21 (ddd, 2J H-P,trans ) 104.3
Hz, 2J H-P,cis ) 19.6 Hz, 2J H-H ) 4.4 Hz, 1H, Ir-H), -9.23 (ddd,
mixture became almost colorless and the solvent was removed
under vacuum to afford 12 as an off-white powder. Yield: 72
mg (97%). IR (Nujol): νIr-H 2123 cm-1
.
31P{1H} NMR (C6D6):
2
2
δ -23.8 (t, J P-P ) 17.8 Hz, 1P), -16.3 (d, J P-P ) 17.8 Hz,
2J H-P,cis ) 14.1 Hz, J H-P,cis ) 21.8 Hz, J H-H ) 4.4 Hz, 1H,
2P). 1H NMR (C6D6): δ -11.27 (dt, J H-P,trans ) 126.5 Hz,
2
2
2
3
Ir-H), 1.33 (t, J H-H ) 7.4 Hz, 9H, CH3-CH2S), 2.91 (m, 6H,
2J H-P,cis ) 19.0 Hz, 1H, Ir-H), 1.20 (t, 3J H-H ) 7 Hz, 9H, CH3-
CH2O), 3.80 (q, 3J H-H ) 7 Hz, 6H, CH2O), 1.12 (overlapped m,
27H, PCH2-CH3), 2.11 (app quin, J ) 7.3 Hz, 6H, unique
P-CH2-CH3), 2.15 and 2.30 (symmetrical pattern consisting
of two 13-line multiplets, 6H each, mutually trans P-CH2-
CH3). FD-MS: m/z 746 (M+, 193Ir).
CH2S), 6.8-7.6 (several m, 30H, C6H5-P).13C{1H} NMR
2
2
(C6D6): δ 179.8 (dd, J C-P,cis ) 7.4 Hz, J C-P,cis ) 4.2 Hz, Ir-
CO).
P r ep a r a tion of fa c-(P Me3)3Ir (CH3)(H)(Si(SEt)3) (6). To
a solution of 25 mg (0.05 mmol) of CH3Ir(PMe3)4 in 1 mL of
C6H6 was added 10 µL (0.05 mmol) of HSi(SEt)3 at room
temperature. The yellow color of the solution immediately
disappeared. The reaction mixture was filtered from a small
amount of a precipitate, and 31P{1H} NMR of the filtrate
indicated clean formation of 6 and liberation of 1 equiv of
PMe3. The solvent was removed under vacuum to yield 26
mg (80%) of 6 as colorless plates. Anal. Calcd for C16H46IrP3S3-
Si: C, 29.66; H, 7.16. Found: C, 29.36; H, 7.17. 31P{1H} NMR
P r ep a r a tion of tr a n s-(P Et3)2Ir (H)(Cl)(Si(OEt)3) (13).
To an orange solution of 62 mg (0.126 mmol) of Ir(PEt3)2(C2H4)-
Cl in 4 mL of pentane was dropwise added upon stirring a
solution of 21 mg (0.128 mmol) of HSi(OEt)3 in 2.5 mL of
pentane. After 30 min the solution became yellow and the
solvent was evacuated to yield 76 mg (96%) of 13 as a yellow-
brownish oil. IR (Nujol): νIr-H ) 2200 cm-1
.
31P{1H} NMR
2
(C6D6): δ 24.0 (s). 1H NMR (C6D6): δ -21.62 (t, J H-P,cis
)
3
(C6D6): δ -61.0 (pseudo t, J ) 20.2 Hz, 1P), -59.7 (dd, J 1
)
12.7 Hz, 1H, Ir-H), 1.22 (t, J H-H ) 7 Hz, 9H, CH3-CH2O),
3
17.2 Hz, J 2 ) 19.6 Hz, 1P), -57.1 (dd, J 1 ) 17.2 Hz, J 2 ) 20.7
3.92 (q, J H-H ) 7 Hz, 6H, CH2O), 1.06 (app quin, J ) 7.6 Hz,
2
Hz, 1P). 1H NMR (C6D6): δ -12.35 (ddd, J H-P,trans ) 124.5
18H, PCH2-CH3), 1.97 (m, 12H, P-CH2-CH3). 13C{1H} NMR
(C6D6): δ 8.78 (s, PCH2-CH3), 17.85 (vt, J ) 16.2 Hz, P-CH2-
CH3), 18.39 (s, CH3-CH2O), 58.23 (s, CH3-CH2-O). FD-MS:
m/z 628 (M+, 193Ir).
2
2
Hz, J H-P,cis ) 21.8 Hz, J H-P,cis ) 13.6 Hz, 1H, Ir-H), 0.51
3
3
3
(dddd, J H-P,trans ) 11.5 Hz, J H-P,cis ) 10.2 Hz, J H-P,cis ) 4.4
Hz, 3J H-H ) 1.2 Hz, 3H, Ir-CH3), 1.02 (d, 2J H-P ) 7.7 Hz, 9H,
2
2
CH3-P), 1.33 (d, J H-P ) 7.9 Hz, 9H, CH3-P), 1.58 (d, J H-P
P r oced u r es of Hyd r olysis Exp er im en ts. The pure
complexes were subjected to high vacuum prior to use to
ensure that no traces of easily hydrolyzable silanes would be
present at the next stage.
(a) Complexes 5-7 (0.02 mmol) were dissolved in a mixture
containing 0.1 mL (about 280 equiv) of H2O and 0.4 mL of
THF. No changes were observed in 31P NMR after 1 day. Then
3 equiv of NaOH as a 1 M solution in H2O was added to every
sample. After 10 h the reaction mixtures were checked by 31P
NMR again to show no observable changes.
(b) Complex 9 (0.02 mmol) was treated with 5 equiv of H2O
in 0.5 mL of C6D6. After 3 h of stirring, the white precipitate
that was formed was filtered off and the filtrate containing
pure 10 was identified by its 31P and 1H NMR. The solvent
was removed under vacuum to afford 10 in almost quantitative
yield.
(c) Complexes 12 and 13 (0.1 mmol) were dissolved in 1,4-
dioxane (2 mL) and to the resulting solutions was added 50
µL of H2O (about 28 equiv). 31P NMR spectra of the mixtures
showed no changes after 12 h. Then an additional 100 µL of
H2O was added to each of the samples, and the mixtures were
heated in closed vessels at 80 °C for 12 h. Under these
conditions white precipitates were formed. These were re-
moved by filtration, the filtrates were evacuated, and the
residues formed were redissolved in C6D6. NMR analysis
showed clean formation of mer,cis-(PEt3)3IrH2Cl (14)20 in the
case of 12, while 13 decomposed to a complicated mixture,
containing 14 along with some other unidentified compounds.
The systems were not investigated further.
3
) 8.0 Hz, 9H, CH3-P), 1.48 (t, J H-H ) 7.4 Hz, 9H, CH3-
CH2S), 3.12 (m, 6H, CH2S).
P r ep a r a tion of m er -(P Me3)3Ir (C6F 5)(H)(Si(SEt)3) (7)
a n d m er -(P Me3)3Rh (C6F 5)(H)(Si(SEt)3) (9). These com-
plexes were prepared similarly to mer-(PMe3)3Rh(C6F5)(H)(Si-
(OEt)3) (11), which was fully characterized.7
Characterization of 7: colorless solid, yield 95%. 31P{1H}
4
4
NMR (C6D6): δ -65.4 (ddt, J P-F ) 26.3 Hz, J P-F ) 38.3 Hz,
2J P-P ) 22.0 Hz, 1P), -53.7 (d, 2J P-P ) 22.0 Hz, 2P). 1H NMR
(C6D6): δ -12.0 (app dq, J H-P,trans ) 132 Hz, J H-P,cis ) 4J H-F
2
2
) 13 Hz, 1H, Ir-H), 1.33 (vt, J ) 3.6 Hz, 18H, CH3-P), 1.49
2
3
(d, J H-P ) 7.6 Hz, 9H, CH3-P), 1.40 (t, J H-H ) 7.4 Hz, 9H,
CH3-CH2S), 3.00 (q, 3J H-H ) 7.4 Hz, 6H, CH2S). 19F{1H} NMR
(C6D6): δ -95.5 (m, 1F, ortho), -102.4 (tt, J 1 ) 9.6 Hz, J 2
)
37.6 Hz, 1F, ortho), -160.1 (t, J ) 20.6 Hz, 1F, para), -160.4
(m, 1F, meta), -161.3 (m, 1F, meta). FD-MS: m/z 800 (M+,
193Ir).
Characterization of 9: slightly yellow solid, yield 93%. 31P-
{1H} NMR (C6D6): δ -30.0 (dm, 1J P-Rh ) 85.9 Hz, 2J P-P ) 30.7
1
2
Hz, 1P), -11.0 (dd, J P-Rh ) 94 Hz, J P-P ) 30.8 Hz, 2P). 1H
2
NMR (C6D6): δ -9.77, (dm, J H-P,trans ) 164.3 Hz, 1H, Rh-
2
H), 1.17 (vt, J ) 3.3 Hz, 18H, CH3-P), 1.33 (br d, J H-P ) 7.1
Hz, 9H, CH3-P), 1.37 (t, 3J H-H ) 7.5 Hz, 9H, CH3-CH2S), 3.00
(q, 3J H-H ) 7.5 Hz, 6H, CH2S). 19F{1H} NMR (C6D6): δ -95.9
(m, 1F, ortho), -101.4 (tt, J 1 ) 11.8 Hz, J 2 ) 40.4 Hz, 1F,
ortho), -159.5 (t, J ) 20.7 Hz, 1F, para), -160.0 (m, 1F, meta),
-160.9 (m, 1F, meta).
P r ep a r a tion of m er -(P Me3)3Rh (C6F 5)(H)(SEt) (10).
A
bright yellow solution of 15 mg (0.03 mmol) of C6F5Rh(PMe3)3
in 0.5 mL of C6D6 was treated with 225 µL of a 0.135 M
solution of HSEt in C6D6. The color of the solution changed
to slightly yellow, and NMR analysis indicated quantitative
formation of 10, which was isolated after removal of the solvent
under vacuum in 95% yield as a yellow solid. Anal. Calcd
for C17H33F5P3RhS: C, 36.44; H, 5.94. Found: C, 36.14; H,
6.01. 31P{1H} NMR (C6D6): δ -31.5 (m, 2J P-P ) 28.0 Hz, 1P),
Sila n e Exch a n ge Exp er im en ts. Complexes 5, 7, and 9
were all treated as described below. To a solution of the
complex (0.02 mmol) in 0.5 mL of C6D6 was added by a
microsyringe 0.2 mmol of HSi(OEt)3. The reaction mixture
was kept at room temperature and was periodically monitored
by 31P and 1H NMR spectroscopy. No change in the NMR
spectra was detected after 2 days for complexes 5 and 7, while
in the case of complex 9 80% conversion to the known mer-
(C6F5)(H)(Si(OEt)3)Rh(PMe3)3 (11)7 along with formation of free
HSi(SEt)3 was observed.
1
2
-9.0 (dd, J P-Rh ) 98.2 Hz, J P-P ) 28.0 Hz, 2P). 1H NMR
(C6D6): δ -10.00 (dm, 2J H-P,trans ) 194.3 Hz, 1H, Rh-H), 1.03
2
(d, J H-P ) 7.5 Hz, 9H, CH3-P), 1.05 (vt, J ) 3.2 Hz, 18H,
3
CH3-P), 1.50 (t, J H-H ) 7.6 Hz, 3H, CH3-CH2S), 2.59 (q,
Ack n ow led gm en t. This work was supported by the
Israel Science Foundation, J erusalem, Israel, and by the
MINERVA Foundation, Munich, Germany.
3J H-H ) 7.6 Hz, 2H, CH2S). 19F{1H} NMR (C6D6): δ -97.2
(m, 1F, ortho), -107.2 (m, 1F, ortho), -162.1 (m, 1F, meta),
-162.4 (t, J ) 20.7 Hz, 1F, para), -163.0 (m, 1F, meta).
P r ep a r a tion of m er -(P Et3)3Ir (H)(Cl)(Si(OEt)3) (12). To
a red solution of 58 mg (0.100 mmol) of Ir(PEt3)3Cl in 1 mL of
pentane was added dropwise upon stirring a solution of 22 mg
(0.134 mmol) of HSi(OEt)3 in 2 mL of pentane. After 1 h the
OM950791R
(20) Complex 14 was easily identified by its 31P and 1H NMR, see:
Blum, O.; Milstein, D. J . Am. Chem. Soc. 1995, 117, 4582 and
references therein.