Iridium- and rhodium-silanol complexes: Synthesis and reactivity

Article abstract of DOI:10.1021/om0300427

Methods of metallo-silanol synthesis have been developed. The Ir(I) complex (Et₃P)₂Ir(C₂H₄)Cl (1) oxidatively adds secondary silanols R₂SiHOH (R = ⁱPr, ^tBu) to yield the iridium-silanol complexes [(Et₃P)₂Ir(H)(Cl)(SiR₂OH)] (R = ⁱPr, 2; R = ^tBu, 3). The crystal structure of 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogen bonding is present. Deprotonation of 2 results in the highly thermodynamically stable metallo-silanolate [(Et₃P)₂Ir(H)(Cl) (SiⁱPr₂OLi)]₂ (4). Compound 4 has an almost planar core, consisting of two atoms each of iridium, silicon, chlorine, oxygen, and lithium. Upon treatment of (Et₃P)₃RhCl with HSiⁱPr₂OH, the first Rh-silanol complex, trans-[(Et₃P)₂Rh(H)(Cl)(ⁱPrSi₂OH)], is formed in an equilibrium with the starting complex (K_eq = 4 × 10^-3); hence, the reaction is dependent on the concentration of the silanol and Et₃P, an excess of the latter shifting the equilibrium to the starting compounds. Reaction of the bis-phosphine complex [(Et₃P)₂RhCl]₂ with the silanol, which does not generate free phosphine, results in 96% conversion to the adduct. On the other hand, the chelating bis-phosphine complex [(bis-(diisopropylphosphino)propane)RhCl]₂ does not add the silanol even in the presence of a 10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct is unfavorable. In contrast to the Et₃P-containing Ir complex, and similarly to the Rh complex, (PPh₃)₃Ir(CO)H reacts with ⁱPr₂SiHOH reversibly, leading to 60% conversion to the metallosilanol (PPh₃)₂Ir(CO)(H)₂(SiⁱPr₂O H) (6). A stable PPh₃-containing Ir-silanol was prepared by starting from (PPh₃)₂Ir(CO)(H)₂(Si(SEt)₃). Following reaction with Et₃SiOSO₂CF₃ to exchange one SEt substituent with OSO₂CF₃, reaction with NaOH generates the stable silanol complex (PPh₃)₂Ir(CO)(H)₂(Si(SEt)₂OH) (14).

Full text of DOI:10.1021/om0300427

4020
Organometallics 2003, 22, 4020-4024
Ir id iu m - a n d Rh od iu m -Sila n ol Com p lexes: Syn th esis
a n d Rea ctivity
Roman Goikhman, Michael Aizenberg, Linda J . W. Shimon, and David Milstein*
Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel 76100
Received J anuary 21, 2003
Methods of metallo-silanol synthesis have been developed. The Ir(I) complex (Et3P)2Ir-
(C2H4)Cl (1) oxidatively adds secondary silanols R2SiHOH (R ) iPr, tBu) to yield the iridium-
i
t
silanol complexes [(Et3P)2Ir(H)(Cl)(SiR2OH)] (R ) Pr, 2; R ) Bu, 3). The crystal structure
of 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogen
bonding is present. Deprotonation of 2 results in the highly thermodynamically stable
metallo-silanolate [(Et3P)2Ir(H)(Cl)(SiiPr2OLi)]2 (4). Compound 4 has an almost planar core,
consisting of two atoms each of iridium, silicon, chlorine, oxygen, and lithium. Upon treatment
of (Et3P)3RhCl with HSiiPr2OH, the first Rh-silanol complex, trans-[(Et3P)2Rh(H)(Cl)(iPrSi2-
OH)], is formed in an equilibrium with the starting complex (Keq ) 4 × 10-3); hence, the
reaction is dependent on the concentration of the silanol and Et3P, an excess of the latter
shifting the equilibrium to the starting compounds. Reaction of the bis-phosphine complex
[(Et3P)2RhCl]2 with the silanol, which does not generate free phosphine, results in 96%
conversion to the adduct. On the other hand, the chelating bis-phosphine complex [(bis-
(diisopropylphosphino)propane)RhCl]2 does not add the silanol even in the presence of a
10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct is
unfavorable. In contrast to the Et3P-containing Ir complex, and similarly to the Rh complex,
i
(PPh3)3Ir(CO)H reacts with Pr2SiHOH reversibly, leading to 60% conversion to the metallo-
silanol (PPh3)2Ir(CO)(H)2(SiiPr2OH) (6). A stable PPh3-containing Ir-silanol was prepared
by starting from (PPh3)2Ir(CO)(H)2(Si(SEt)3). Following reaction with Et3SiOSO2CF3 to
exchange one SEt substituent with OSO2CF3, reaction with NaOH generates the stable
silanol complex (PPh3)2Ir(CO)(H)2(Si(SEt)2OH) (14).
In tr od u ction
the corresponding silyl complexes or by oxyfunctional-
ization of a Si-H fragment bound to a metal center with
dimethyldioxirane.3-5
We communicated the synthesis of metallo-silanol
complexes by the direct oxidative addition of secondary
silanols to transition-metal complexes.6,7 In this paper
we describe a complete study on the preparation of
iridium- and rhodium-silanol complexes with different
phosphine and silyl ligands.
Organic silanols have been extensively studied.1
These compounds are intermediates in the formation
of various organosilicon compounds, including important
silicone polymers.2 In contrast, metallo-silanols,3-7 i.e.,
compounds that contain a M-Si-OH moiety, form a
relatively new class of compounds which has attracted
attention only recently. These complexes, being inter-
esting as such, can also potentially be synthetically
useful. For example, they may find applications in
metallo-functionalized silica and organometallic poly-
mers. Metallo-silanols, which are still limited in num-
ber, were reported to be formed either by hydrolysis of
Resu lts a n d Discu ssion
Treatment of trans-(Et3P)2Ir(C2H4)Cl8a (1) (or its
precursor (Et3P)2Ir(C2H4)2Cl)8b with 1 equiv of R2SiHOH
i
(R ) Pr,9 tBu10) at room temperature led to formation
* To whom correspondence should be addressed. Fax: 972-8-
9344142. E-mail: david.milstein@weizmann.ac.il.
(1) Mittal, K. L., Ed. Silanes and Other Coupling Agents; VSP:
Utrecht, The Netherlands, 1992.
of the coordinatively unsaturated metallo-silanols
[(Et3P)2Ir(H)(Cl)(SiR2OH)] (eq 1).
(2) Noll, W. Chemistry and Technology of Silicones; VCH: Wein-
heim, Germany, 1968.
(3) Chang, L. S.; J ohnson, M. P.; Fink, M. J . Organometallics 1991,
10, 1219.
(4) Rickard, C. E. F.; Roper, W. R.; Salter, D. M.; Wright, L. J . J .
Am. Chem. Soc. 1992, 114, 9682.
(5) (a) 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. (b)
For recent publications on the subject see: Malisch, W.; Hofmann, M.;
Kaupp, G.; Kab, H.; Reising, J . Eur. J . Inorg. Chem. 2002, 3235 and
references therein.
(6) Goikhman, R.; Aizenberg, M.; Kraatz, H. B.; Milstein, D. J . Am.
Chem. Soc. 1995, 117, 5865.
(7) Goikhman, R.; Aizenberg, M.; Shimon, L. J . W.; Milstein, D. J .
Am. Chem. Soc. 1996, 118, 10894.
Complex 2 was characterized by X-ray analysis (see
ref 6 for details). The fact that the coordinatively
10.1021/om0300427 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 08/30/2003

Iridium- and Rhodium-Silanol Complexes
Organometallics, Vol. 22, No. 20, 2003 4021
unsaturated 16-electron d6 complex 2 has a trigonal-
bipyramidal, rather than a square-pyramidal, configu-
ration may be explained by the presence of the π-donor
chloride ligand.11 Surprisingly, an intermolecular rather
than an intramolecular hydrogen bond between the
chloride and the silanol hydrogen is observed.
Treatment of 2 with tBuLi or nBuLi resulted in
deprotonation, generating the metallo-silanolate [(Et3P)2-
Ir(H)(Cl)(SiiPr2OLi)]2 (4) (eq 2).
fold excess of iPr2SiHOH shifted the equilibrium to the
right, resulting in 97% adduct formation.
The NMR data of 6 are similar to those of other silyl
complexes previously obtained with 5.14 Although the
complex is stable in solution at room temperature in
the presence of an excess of diisopropylsilanol, attempts
to isolate it either by precipitation or by solvent evapo-
ration resulted in decomposition to the starting com-
pounds. Above 50 °C, slow decomposition of 6 to the
starting complex 5 occurred as a result of condensation
of the free silanol to form the inactive tetraisopropyld-
isiloxane, shifting the equilibrium (eq 3) to the left. The
t
bulkier silanol Bu2SiHOH did not give any observable
adduct with 5.
The more reactive unsaturated methyl complex trans-
(PPh3)2Ir(CO)Me (7) reacted with the silanols in a
different manner. Reaction with 1 equiv of the silanol
i
at room temperature required 1 day for Pr2SiHOH and
t
5 days for Bu2SiHOH and resulted in mixtures, the
most significant product being the hydride complex 5.
Signals at 0.04 and -0.02 ppm, detected in the 1H NMR
i
t
of the reaction mixtures of 7 with Pr2SiHOH and Bu2-
SiHOH, may be attributed respectively to iPr2MeSiOH
and Bu2MeSiOH. Apparently, Si-H oxidative addition
t
to 7 was followed by Me-Si reductive elimination,
resulting in the Ir(I) hydride complexes.15 Competitive
C-H and C-Si reductive elimination from Ir(III) was
reported by our group.15 It was shown that C-Si
reductive elimination can occur when alkyl-substituted
silyl ligands are employed, as observed here as well.
Addition of an excess of the silanols to 7 resulted in
formation of dihydrido silyl complexes (eq 4). Reaction
Complex 4 crystallizes as a centrosymmetric dimer
with a near-planar core, consisting of two atoms each
of iridium, silicon, chlorine, oxygen, and lithium (see ref
6 the for X-ray structure). The Li-O bond lengths and
Li‚‚‚Li contacts in the Li-O-Li-O square are among
the shortest known.12 The metallo-silanolate dimer 4
exhibites outstanding thermodynamic stability in solu-
tion, and remarkably, it is formed even at the expense
of extraction of Li+ from a crown ether. Thus, when
[Li(12-crown-4)2][CHPh2]13 was used as a base, the
silanolate 4 and liberated 12-crown-4 were formed
quantitatively. Complex 4 reacted instantaneously with
water, yielding the parent compound 2.
Whereas the triethylphosphine Ir(I) complexes form
stable Ir(III) adducts with secondary silanols, triphen-
ylphosphine monocarbonyl Ir(I) complexes show differ-
ent reactivity.
of 7 with a 4-fold excess of tBu2SiHOH required 10 days
at room temperature in C6D6 for completion and re-
sulted in formation of the dihydride complex 8 as a
major product (about 80% yield by NMR), which is the
analogue of 6.16 Some amount of complex 5 was also
formed as a byproduct, being a phosphine adduct of the
intermediate Ir(I) hydride complex.
Treatment of (PPh3)3Ir(CO)H (5) with a stoichiometric
i
amount of Pr2SiHOH resulted in only a partial (60%)
conversion to the metallo-silanol 6 (eq 3). Using a 10-
The fact that 8 was formed in reaction 4 while it was
t
not formed in the reaction of Bu2SiHOH with 5 (see
above) can be explained by the presence of a free 1 equiv
of phosphine in the latter case (compare with eq 3). As
in the case of complex 6, complex 8 is stable only in the
t
presence of excess Bu2SiHOH.
Thus, the direct oxidative addition of two secondary
dialkylsilanols to the triphenylphosphine Ir(I) complexes
5 and 7 led to reversible formation of Ir(III)-silanol
adducts, which were observed in solution in the presence
of an excess of the silanol substrates. We then examined
(8) (a) Aizenberg, M.; Milstein, D.; Tulip, T. H. Organometallics
1996, 15, 4093. (b) Casalnuovo, A. L.; Calabrese, J . C.; Milstein, D.
Inorg. Chem. 1987, 26, 971.
(9) Gilman, H.; Clark, R. N. J . Am. Chem. Soc. 1947, 69, 1499.
(10) Barton, T. J .; Tully, C. R. J . Organomet. Chem. 1979, 172, 11.
(11) Stabilization of one configuration over another due to a partial
multiple bond between the metal center and the π-donor was predicted
by theoretical studies: Poulton, J . T.; Sigalas, M. P.; Folting, K.; Streib,
W. E.; Eisenstein, O.; Caulton, K. Inorg. Chem. 1994, 33, 1476 and
references therein.
(14) Harrod, J . F.; Gilson, D. F. R.; Charles, R. Can. J . Chem. 1969,
47, 2205.
(15) Aizenberg, M.; Milstein, D. Angew. Chem., Int. Ed. Engl. 1994,
33, 317.
(12) Review on X-ray structures of organolithium compounds: Set-
zer, W. N.; Schleyer, P. v. R. Adv. Organomet. Chem. 1985, 24, 353.
(13) Olmstead, M. M.; Power, P. P. J . Am. Chem. Soc. 1985, 107,
2174.
(16) C-Si reductive elimination products were formed in less than
equivalent amounts according to integration of signals in 1H NMR.
Parallel reactions leading to the same Ir products probably take place.
These reactions are under investigation.

4022 Organometallics, Vol. 22, No. 20, 2003
Goikhman et al.
Ta ble 1. 31P NMR Ch em ica l Sh ifts (δ) of P P h 3
the possibility of synthesizing stable (triphenylphos-
phine)iridium-silanol species by a reaction of the silyl
ligand.
Tr a n s to Silyl Liga n d
X in P-Ir-X
As we have reported,17 treatment of 5 with the tris-
(ethylthio)silane (EtS)3SiH resulted in the adduct 9 in
quantitative yield (eq 5).
Si(tBu)2OH Si(iPr)2OH Si(SEt)3 Si(SEt)2OH Si(SEt)2OTf
-0.53
1.60
1.88
1.98
2.72
13 with 1 equiv of NaOH in a THF/water solution
resulted in the immediate formation of the new metallo-
silanol complex 14 (eq 7).
Complex 9 is stable in solution and in the solid state
at room temperature. Interestingly, this compound may
also be synthesized from Vaska’s complex (10) and 2
equiv of the thiosilane. The route of the latter reaction
(eq 6) involves most probably initial formation of the
Complex 14 also has two nonequivalent SEt groups,
according to 1H NMR data. It is a stable colorless
compound, which is completely inert toward an excess
of water or NaOH, similarly to its precursor 9.
It is worth noting that the 31P NMR spectra of the
new complexes indicate a downfield shift of the signals
of the phosphine trans to the silyl group in the order
depicted in Table 1. This dependence corresponds to the
expected increase of electrophilicity of the silicon atom.
In order to compare Ir and Rh chemistry, (Et3P)3RhCl
was treated with HSiiPr2OH, producing the first Rh-
silanol complex, [(Et3P)2Rh(H)(Cl)(SiiPr2OH)] (15). The
reaction is reversible, and addition of either silanol or
triethylphosphine shifted the equilibrium to the prod-
ucts or to the starting compounds, respectively; Keq ) 4
× 10-3 (273 K). It is noteworthy that an excess of Et3P
caused breaking of the relatively strong Rh-H and Rh-
Si bonds in favor of reductive elimination of the weak
H-Si bond, undoubtedly driven by formation of a strong
Rh(I)-PEt3 bond.
The similar bis-phosphine complex [(Et3P)2RhCl]2
reacted with a stoichiometric amount of the silanol,
resulting in 96% conversion to the adduct 15. Finally,
no reaction was observed between the chelated bis-
phosphine complex [(dippp)RhCl]2 (dippp ) bis(diiso-
propylphosphino)propane) and the silanol, when either
a stoichiometric amount or a 10-fold excess of the silanol
was used. Considering the similarity of both bis-phos-
phine complexes from the electronic and steric points
of view, it is likely that the thermodynamically stable
configuration of the adduct is the trans-phosphine one
(see eq 8), which is unavailable with dippp. This
intermediate adduct 11, which eliminates the (EtS)3SiCl,
giving rise to the unsaturated hydride complex 12
which, in turn, adds 1 equiv more of HSi(SEt)3 to form
the stable dihydride 9. Apparently, the presence of the
weak σ-donor chloride ligand in 11, along with the high
Si-Cl bond strength, makes Si-Cl reductive elimina-
tion favorable.18 Formation of a new compound, which
1
is believed to be (EtS)3SiCl, was indicated by H NMR;
however, attempts to isolate this product failed.
Attempting to prepare a metallo-silanol from complex
9, we first tried to substitute one SEt group for OH with
NaOH in a water/THF solution, but no hydrolysis
occurred.17 Applying another approach, complex 9 was
treated with a stoichiometric amount of Et3SiOTf in
pentane at room temperature, leading to selective
substitution of one SEt group by the triflate anion
(eq 7). An analogous reaction was demonstrated by
Tilley with ruthenium and platinum thiosilyl com-
plexes.19 The reaction was slow but resulted in high
yield and the product complex 13 precipitated from a
pentane solution. An analogous, faster reaction took
place with Me3SiOTf, but the reaction was less selective,
forming about 15% of byproducts.
Interestingly, while all the SEt groups in 9 are
equivalent, the two SEt groups in complex 13 exhibit
1
two different signals in H NMR. Treatment of complex
(17) Aizenberg, M. Goikhman, R. Milstein, D. Organometallics 1996,
15, 1075.
(18) Formation of ClSiR3 as a product of reaction of late-transition-
metal chlorides with HSiR3 is known. See for example: Haszeldine,
R. N.; Malkin, L. S.; Parish, R. V. J . Organomet. Chem. 1979, 182,
323.
(19) Grumbine, S. K.; Mitchell, G. P.; Straus, D. A.; Tilley, T. D.;
Rheingold, A. L. Organometallics 1998, 17, 5607 and references
therein.

Iridium- and Rhodium-Silanol Complexes
Organometallics, Vol. 22, No. 20, 2003 4023
tr a n s-[(Et3P )2(H)Ir (Cl)(SiiP r 2OH)] (2). A solution of 40
mg (0.08 mmol) of (Et3P)2Ir(C2H4)(Cl) (1) in 0.5 mL of C6D6
was treated with 12.5 µL (0.08 mmol) of iPr2Si(H)OH at room
temperature. A rapid change of color of the solution from
orange to yellow was observed. Yellow crystals of 2 were
obtained in quantitative yield after removal of the solvent in
vacuo.
structure was confirmed by 13C NMR measurement of
complex 15. The P-CH2 signal appears as a virtual
triplet, in analogy to the P-CH2 signal in the 13C NMR
spectrum of complex 2. In addition, 29Si NMR of 15
confirmed the cis orientation of the silyl ligand with
regard to the two phosphines.20
In conclusion, a series of iridium-silanol complexes
bearing different ligands were synthesized, using dif-
ferent approaches, and were fully characterized. The
PEt3-containing Ir(I) complexes reacted with secondary
silanols to give stable Ir(III)-silanol complexes. The
analogous reaction of silanols with PEt3-containing Rh-
(I) complexes is reversible, whereas chelating bis-
phosphine Rh(I) complexes were unreactive. The
Ir(III)-silanols can be converted to stable metallosil-
anolates by deprotonation with Li alkyls. The crystal-
lographically characterized iridiasilanolate exhibits an
interesting, very stable Li-bridged dimeric structure.
Remarkably, this compound can be formed even by
extraction of Li+ from its crown ether complex. The less
electron rich, similar PPh3-containing iridium carbonyl
adducts with bulky dialkylsilanols are unstable and
exist only in the presence of an excess of the silanol
substrate, similarly to the Rh silanols. A stable PPh3
carbonyl iridium-silanol complex was synthesized by
stepwise substitution of the SEt group in the Si(SEt)3
ligand by a triflate group and then by hydroxide. In
general, this stepwise substitution of suitable substit-
uents at a silyl ligand seems to be a useful method for
the preparation of metallo-silanol complexes, especially
when the desired secondary silanols are not available,
or in cases where they do not form stable adducts with
metal complexes.
1
NMR (C6D6): 31P{1H}, 19.14 s; H, 1.85 m (CH2-P, 12H),
3
1.23 d, overlapped with 1.21 d (like quasi-t, J H-H ) 7.2 Hz,
CH3CHSi, 12H total), 1.09 m (CHSi, 2H), 1.01 vtt (quasi-quin,
|J observed| ) 7.5 Hz, CH3CH2P, 18H), -20.82 t (2J H-Pcis ) 13.6
2
Hz; HIr, 1H) (the OH signal is obscured by other peaks); D-
{1H} (after exchange with D2O in benzene), 1.00 br s (IrSiOD),
-20.8 br s (IrD, traces); 13C{1H}, 20.49 s (CHSi), 20.25 s (CH3-
1
CHSi), 19.53 s (CH3CHSi), 18.32 vt (| J CP + 3J CIrCP| ) 15.7 Hz,
CH2P), 8.77 s (CH3CH2P); 29Si{1H}, 19.57 t (2J Si-Pcis ) 26 Hz).
IR data (Nujol): 3485 cm-1 (br, O-H). Anal. Calcd for C18H46
ClIrOP2Si: C, 36.26; H, 7.78. Found: C, 36.53; H, 8.15.
-
tr a n s-(Et3P )2(H)Ir (Cl)(SitBu 2OH) (3). A solution of 40 mg
(0.08 mmol) of 1 in 3 mL of pentane was treated with 13 mg
(0.08 mmol) of tBu2Si(H)OH at room temperature. The reaction
mixture was stirred overnight, and then the solvent was
evaporated. The residue was washed with 2 × 0.5 mL of cold
pentane. The metallo-silanol 3 was obtained in 62% yield (31
mg) as small orange crystals. NMR (C6D6): 31P{1H}, 19.7 and
10.6 (AB quartet, 2J P-Ptrans ) 335 Hz); 1H, 1.9 m (CH2P, 12H),
1.36 br.s. (CH3CSi, 9H), 1.18 m (OH, 1H) 1.08 br s (CH3CSi,
2
9H), 1.0 m (CH3CH2P, 18H), -21.02 t (| J H-Pcis| ) 14 Hz; H-Ir,
1H); 13C{1H}, 31.22 s (CH3CSi), 30.49 s (CH3CSi), 26.16 s (CSi),
1
25.61 s (CSi), 18.56 vt (| J CP + 3J CIrCP| ) 29 Hz, CH2P), 8.88 s
(CH3CH2P), 8.34 s (CH3CH2P).
[(Et3P )2(H)Ir (Cl)(SiiP r 2OLi)]2 (4). A solution of 30 mg
(0.05 mmol) of 2 in 1 mL of pentane was treated with 34 µL of
a 15% pentane solution of tBuLi or nBuLi (0.05 mmol) at 0 °C.
The resulting solution was carefully concentrated under
vacuum to ∼30% of the initial volume and cooled to -30 °C.
Small yellow crystals of 4 precipitated over 1 day. They were
separated from the solution in 90% yield. NMR (C6D6): 31P-
{1H}, 16.95 s; 1H, 1.83 m (CH2P, 12H), 1.60 d (3J H-H ) 7.5 Hz,
CH3CHSi, 6H), 1.35 d (3J H-H ) 7.5 Hz, CH3CHSi, 6H), 1.06
vtt (quasi-quin, |J observed| ) 7.5 Hz, CH3CH2P, 18H), 1.0 m
(CHSi, 2H), -20.92 t (2J H-Pcis ) 15.7 Hz; HIr, 1H); 13C{1H},
24.42 s (CH3CHSi), 20.88 s (CH3CHSi), 20.05 br s (CHSi), 18.02
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. Solvents were purified
by standard procedures, degassed, and stored over molecular
sieves in the glovebox. All the reagents were of reagent grade.
NMR spectra were obtained with a Bruker AMX 400 spec-
trometer at ambient probe temperature in C6D6 solutions
unless otherwise specified. NMR chemical shifts are reported
in ppm and are referenced to internal residual C6D5H at δ 7.15
(1H NMR, 400 MHz) or external 85% H3PO4 in D2O at δ 0.0
(31P NMR, 162 MHz). Abbreviations are as follows: s, singlet;
d, doublet; t, triplet; q, quartet; m, multiplet; br, broad; v,
virtual. IR spectra were measured with a Nicolet-510 FT-IR
spectrometer. IR samples were prepared in the glovebox using
cell holders featuring O-rings. They were measured as Nujol
mulls on NaCl plates. Elemental analyses were performed at
Kolbe Laboratorium, Mulheim, Germany. The following com-
1
3
vt (| J CP + J CIrCP| ) 15.0 Hz, CH2P), 8.97 d (2J C-P ) 3.7 Hz,
CH3CH2P); 29Si{1H}, 3.74 t (2J Si-Pcis ) 15 Hz); 7Li{1H}, 1.76 s.
Anal. Calcd for C18H45ClLiIrOP2Si: C, 35.90; H, 7.53. Found:
C, 36.07; H, 7.91.
[(P h 3P )2(H)2Ir (CO)(SiiP r 2OH)] (6). A solution of 30 mg
(0.03 mmol) of 5 in 0.5 mL of C6D6 was treated with 46 µL
(0.3 mmol) of iPr2Si(H)OH at room temperature. Under these
conditions 97% conversion of 5 to 6 was observed (by NMR).
The adduct 6 was characterized only in solution. Attempts to
isolate this complex either by precipitation or by removal of
solvents resulted in decomposition to starting compounds.
NMR (C6D6): 31P{1H}, 8.5 d (2J P-P ) 13 Hz, PIrH, 1P), 1.6 d
(2J P-P ) 13 Hz, PIrSi, 1P); 1H, 7.50 m (PhP, 6H), 7.38 m (PhP,
6H), 7.03 m (PhP, 9H), 6.90 m (PhP, 9H), 1.65 m (CHSi, 1H),
1.51 d (3J H-H ) 7.3 Hz, CH3CHSi, 3H), 1.45 d (3J H-H ) 7.1
Hz, CH3CHSi, 3H), 1.38 m (CHSi, 1H), 1.28 d (3J H-H ) 7.0
Hz, CH3CHSi, 3H), 1.15 d (3J H-H ) 7.0 Hz, CH3CHSi, 3H),
i
pounds were prepared according to reported procedures: Pr2-
SiHOH,9 tBu2SiHOH,10 HSi(SEt)3,21 1,8 5,22a 7,22b 9,17 10,22c
(Et3P)3RhCl,23a [(Et3P)2RhCl]2,23b [(dippp)RhCl]2.23c
2
2
-9.33 ddd (2J H-Pcis ) 23 Hz; J H-Pcis ) 15.7 Hz; J H-H ) 4.2
(20) The 29Si NMR data of 15 are quite typical. For a recent 29Si
NMR report on Rh(III) silyl complexes see: Nishihara, Y.; Takemura,
M.; Osakada, K. Organometallics 2002, 21, 825.
(21) (a) Lambert, J . B.; Shulz, W. J . J . Am. Chem. Soc. 1988, 110,
2201. (b) Wolinsky, L.; Tieckelmann, H.; Post, H. W. J . Org. Chem.
1951, 16, 395.
(22) (a) Wilkinson, G. Inorg. Synth. 1972, 13, 126. (b) Rees, W. M.;
Churchill, M. R.; Li, Y.; Atwood, J . D. Organometallics 1985, 4, 1162.
(c) Sears, J . C. T.; Kubota, M. Inorg. Synth. 1968, 11, 101.
(23) (a) Intille, G. M. Inorg. Chem. 1972, 11, 695. (b) Blekke, J . R.;
Donaldson, A. J . Organometallics 1986, 5, 2401, (c) Fryzuk, M. D.;
Piers, W. E.; Rettig, S. E.; Einstein, F. W. B.; J ones, T.; Albright, T. A.
J . Am. Chem. Soc. 1989, 111, 5709.
Hz, HIrCO, 1H), -10.88 ddd (2J H-Ptrans ) 108.8 Hz; 2J H-Pcis
)
18.7 Hz; 2J H-H ) 4.2 Hz, HIrP, 1H) (the OH signal is obscured
by other peaks).
[(P h 3P )2(H)2Ir (CO)(SitBu 2OH)] (8). A solution of 15 mg
(0.02 mmol) of 7 in 0.5 mL of C6D6 was stirred for 10 days
with 13 mg (0.08 mmol) of tBu2Si(H)OH at room temperature,
resulting in a mixture of 8 and 5 in a ratio of 4:1. The metallo-
silanol 8 was characterized only in solution for the same
reasons mentioned for complex 6. NMR data for 8 (C6D6): 31P-
{1H}, 5.64 d (2J P-P ) 9 Hz, PIrH, 1P), -0.34 d (2J P-P ) 9 Hz,

4024 Organometallics, Vol. 22, No. 20, 2003
Goikhman et al.
1
2
PIrSi, 1P); H, 7.51 m (PhP, 6H), 7.42 m (PhP, 6H), 6.91 m
Hz, HIrCO, 1H), -10.05 ddd (2J H-Ptrans ) 108 Hz, J H-Pcis
)
(PhP, 18H), 1.42 br s (CH3CSi, 9H), 1.26 s (CH3CSi, 9H), -9.38
20.4 Hz, 2J H-H ) 4.2 Hz, HIrP, 1H) (the OH signal is obscured
ddd (2J H-Pcis ) 22.8 Hz; J H-Pcis ) 16.8 Hz; J H-H ) 4.7 Hz,
by other peaks). IR (Nujol): 3260 cm-1. Anal. Calcd for C41H43
IrO2P2S2Si: C, 53.87; H, 4.74. Found: C, 53.44; H, 4.60.
-
2
2
HIrCO, 1H), -10.95 ddd (2J H-Ptrans ) 106.8 Hz; 2J H-Pcis ) 18.0
2
Hz; J H-H ) 4.7 Hz, HIrP, 1H) (the OH signal is obscured by
other peaks).
Rea ction of Va sk a ’s Com p lex (10) w ith HSi(SEt)3. A
solution of 15 mg (0.02 mmol) of 10 in 0.5 mL of C6D6 was
treated with 8 µL (0.05 mmol) of HSi(SEt)3. 31P{1H} NMR of
the resulting solution showed formation of complex 9 as a
single product. 1H NMR (C6D6) exhibited signals of a new
product, which is likely to be ClSi(SEt)3: 2.61 q (3J H-H ) 7.4
Hz, CH2S, 6H), 1.10 t (3J H-H ) 7.4 Hz, CH3CH2S, 3H).
[(Et3P )2(H)Rh (Cl)(SiiP r 2OH)] (15). A solution of 30 mg
(0.04 mmol) of [(Et3P)2RhCl]2 in 0.5 mL of C6D6 was treated
with 12.5 µL (0.08 mmol) of iPr2Si(H)OH at room temperature,
resulting in 96% conversion in 1/2 h. Complex 15 was charac-
terized in solution. It slowly decomposes at room temperature.
[(P h 3P )2(H)2Ir (CO)(Si(SEt)2OTf)] (13). Complex 9 (20 mg,
0.02 mmol) was stirred with Et3SiOTf (4.5 µL, 0.02 mmol) in
a pentane solution for 2 days at room temperature to produce
a colorless precipitate. Then the solvent was decanted and the
residue was washed with pentane and dried, resulting in 16
mg (76%) of the pure complex 13 as a moisture-sensitive solid.
13 has limited stability at room temperature. NMR (C6D6):
31P{1H}, 4.45 d (2J P-P ) 15.7 Hz, PIrH, 1P), 2.72 d (2J P-P
)
1
15.7 Hz, PIrSi, 1P); H, 7.47 m (PhP, 6H), 7.17 m (PhP, 6H),
6.97 m (PhP, 9H), 6.86 m (PhP, 9H), 2.98 m (CH2S, 4H), 1.26
t (3J H-H ) 7.4 Hz, CH3CH2S, 3H), 1.19 t (3J H-H ) 7.4 Hz, CH3-
i
In an analogous reaction of (Et3P)3RhCl with 1 equiv of Pr2-
CH2S, 3H), -9.46 ddd (2J H-Pcis ) 18.8 Hz; J H-Pcis ) 13.6 Hz;
2
Si(H)OH, just 3% conversion to 15 was observed. NMR
(C6D6): 31P{1H}, 25.8 d (1J Rh-P ) 118.8 Hz); 1H, 1.82 m (CH2P,
12H), 1.34 quasi-t (3J H-H ) 7.3 Hz, CH3CHSi, 12H), 1.2 m
(CH3CHSi, 2H), 1.09 br. t (J ) 7.5 Hz, CH3CH2P, 18H), -16.49
2J H-H ) 4.4 Hz, HIrCO, 1H), -10.51 ddd (2J H-Ptrans ) 106 Hz;
2J H-Pcis ) 18.5 Hz; 2J H-H ) 4.4 Hz, HIrP, 1H). Anal. Calcd for
C
42H42F3IrO4P2S3Si: C, 48.22; H, 4.05. Found: C, 49.03; H,
4.52.
[(P h 3P )2(H)2Ir (CO)(Si(SEt)2OH)] (14). Complex 13 (15
dt (1J Rh-H ) 27.2 Hz, J H-P ) 14.6 Hz, H-Rh, 1H) (the OH
2
signal is obscured by other peaks); 13C{1H}, 21.83 s (CHSi),
mg, 0.015 mmol) was dissolved in 0.5 mL of THF and treated
with 60 µL of a 0.25 M aqueous solution of NaOH (0.015
mmol). The solvents were then removed in vacuo, the residue
was extracted with benzene, and the extracts were filtered.
The solvent was removed from the filtrate under vacuum,
yielding 12 mg of the colorless compound 14 in 92% purity
(by NMR). The pure compound was obtained by slow crystal-
20.12 s (CH3CHSi), 19.54 s (CH3CHSi), 17.93 vt (| J CP + 3J CIrCP
|
1
) 13.0 Hz, CH2P), 8.90 s (CH3CH2P); 29Si{1H}, 58.15 dt (1J Rh-Si
2
) 31.4 Hz, J P-Si ) 8.3 Hz).
Ack n ow led gm en t. This work was supported by the
Israel Science Foundation, J erusalem, Israel, by the
Minerva Foundation, Munich, Germany, and by the
Helen and Martin Kimmel Center for Molecular Design.
D.M. is the holder of the Israel Matz Professorial Chair
of Organic Chemistry.
lization from pentane. NMR (C6D6): 31P{1H}, 6.89 d (2J P-P
)
15.1 Hz, PIrH, 1P), 1.98 d (2J P-P ) 15.1 Hz, PIrSi, 1P); 1H,
7.56 m (PhP, 6H), 7.47 m (PhP, 3H), 7.31 m (PhP, 6H), 6.83-
6.97 ov m (PhP, 15H), 2.97 m (CH2S, 4H), 1.45 t (3J H-H ) 7.4
Hz, CH3CH2S, 3H), 1.42 t (3J H-H ) 7.4 Hz, CH3CH2S, 3H),
-9.11 ddd (2J H-Pcis ) 22 Hz, J H-Pcis ) 14.8 Hz, J H-H ) 4.2
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