Addition of water across Si-Ir bonds in iridium complexes with κ-P, P, Si (biPSi) pincer ligands

Article abstract of DOI:10.1021/ic1016774

Electrophiles such as Me⁺, Ag⁺, or protons react with the five-coordinate Ir(III) complex [IrClH(biPSi)] (biPSi = κ-P,P,Si-Si(Me){(CH₂)₃PPh₂}₂) by abstracting its chloride ligand. The resul

Full text of DOI:10.1021/ic1016774

Inorg. Chem. 2010, 49, 10649–10657 10649
DOI: 10.1021/ic1016774
Addition of Water Across Si-Ir Bonds in Iridium Complexes with K-P,P,Si (biPSi)
Pincer Ligands
´
´
´
Alba Garcıa-Camprubı, Marta Martın, and Eduardo Sola*
´
ꢀ
ꢀ
ꢀ
ꢀ
Departamento de Quımica de Coordinacion y Catalisis Homogenea, Instituto de Ciencia de Materiales de Aragon,
CSIC-Universidad de Zaragoza, E-50009 Zaragoza, Spain
Received August 18, 2010
Electrophiles such as Meþ, Agþ, or protons react with the five-coordinate Ir(III) complex [IrClH(biPSi)] (biPSi = κ-P,P,
Si-Si(Me){(CH2)3PPh2}2) by abstracting its chloride ligand. The resulting species can be stabilized by a variety of L
ligands to give the cationic complexes [IrH(biPSi)L2]þ. The derivative [IrH(biPSi)(NCMe)2]þ has been subjected to a
kinetic study regarding the facile dissociations of its acetonitrile ligands. The presence of water changes the course of
the reaction producing dihydride complexes that contain the silanol ligand κ-O,P,P-HOSi(Me){(CH2)3PPh2}2
(biPSiOH). The water activation product [IrH2(biPSiOH)(NCMe)](CF3SO3) undergoes insertion reactions with
-
-
ethylene and phenylacetylene. The use of hydrolyzable fluorinated counterions such as PF6 or BF4 further
modifies the reaction by provoking the incorporation of fluoride at the silicon atom of the former biPSi ligand. The
dihydride resulting after such a process, [IrH2(biPSiF)(NCMe)2]BF4 (biPSiF = κ-P2-FSi(Me){(CH2)3PPh2}2), displays
a trans-chelating diphosphine ligand. When dehydrogenating the Ir center, spontaneously or using ethylene as
hydrogen acceptor, the diphosphine backbone undergoes a Si-C bond cleavage leading to a new Ir(III) species with
κ-P,Si and κ-C,P chelate ligands.
Introduction
for O-H bond splitting, the ligand environment facilitates
the formation of strong new bonds such as C-H.3,5
The addition of water to transition metal complexes is a
key process for challenges such as the catalytic production of
hydrogen1 or the anti-Markovnikov hydration of alkenes.2
Despite its importance, the reported examples of this reaction
are scarce:3 a noteworthy fact when considering the ubiquity
of the water molecule and its easy activation by deprotona-
tion. The lack of examples is attributable, at least in part, to
the exigent thermodynamics of the O-H bond cleavage:
difficult to balance only on the basis of weaker M-H and
M-OH bonds. Probably as a result, some of the successful
water additions to metal complexes involve extra thermo-
dynamic contributions whose origin is the polynuclear nature
of the reaction products or the participation of non-innocent
functional ligands. In the first case, the resulting OH frag-
ment can bridge metals, forming two bonds instead of one.3,4
In the second, in addition to enabling alternative pathways
The present work describes a water addition reaction that
formally benefits from both aforementioned thermodynamic
advantages, since the OH fragment ends up as a bridge
between an iridium center and the silicon atom of a κ-P,P,
Si pincer ligand, which therefore contributes with a strong
Si-O bond.6 This reaction, facile for complex [IrClH(biPSi)]
(biPSi=κ-P,P,Si-Si(Me){(CH2)3PPh2}2) in the presence of
electrophilic reagents, might limit the practical application in
catalysis of silicon-donor pincers: ligands capable of stabiliz-
ing very reactive unsaturated complexes7 with distinctive
structures.8 On the other hand, the reaction leads to new
iridium derivatives with rare silanol pincers or trans-chelating
(5) (a) Kohl, S. W.; Weiner, L.; Schwartsburd, L.; Konstantinovski, L.;
Shimon, L. J. W.; Ben-David, Y.; Iron, M. A.; Milstein, D. Science 2009, 324,
74–77. (b) Li, J.; Shiota, Y.; Yoshizawa, K. J. Am. Chem. Soc. 2009, 131, 13584–
13585. (c) Burn, M. J.; Fickes, M. G.; Hartwig, J. F.; Hollander, F. J.; Bergman.,
R. G. J. Am. Chem. Soc. 1993, 115, 5875–5876; See also:. (d) Salem, H.;
Shimon, L. J. W.; Diskin-Posner, Y.; Leitus, G.; Ben-David, Y.; Milstein, D.
Organometallics 2009, 28, 4791–4806.
*To whom correspondence should be addressed. E-mail: sola@unizar.es.
(1) Hetterscheid, D. G. H.; van der Vlugt, J. I.; de Bruin, B.; Reek, J. N. H.
Angew. Chem., Int. Ed. 2009, 48, 8178–8181.
(2) Borman, S. Chem. Eng. News 2004, 82(11), 42–43.
(3) Ozerov, O. V. Chem. Soc. Rev. 2009, 38, 83–88.
(4) (a) Dorta, R.; Rosenberg, H.; Shimon, L. J. W.; Milstein, D. Chem.;
Eur. J. 2003, 9, 5237–5249. (b) Dorta, R.; Rozenberg, H.; Shimon, L. J.; Milstein,
D. J. Am. Chem. Soc. 2002, 124, 188–189. (c) Tani, K.; Iseki, A.; Yamagata, T.
Angew. Chem., Int. Ed. 1998, 37, 3381–3383. (d) Dorta, R.; Togni, A. Organo-
metallics 1998, 17, 3423–3428.
(6) Becerra, R.; Walsh, R. In The Chemistry of Organic Silicon Com-
pounds; Rappoport, Z., Apeloig, Y., Eds.; Wiley: Chichester, UK, 1998; Vol. 2, pp
153-180.
(7) (a) MacLean, D. F.; McDonald, R.; Ferguson, M. J.; Caddell, A. J.;
Turculet, L. Chem. Commun. 2008, 5146–5148. (b) Morgan, E.; MacLean,
D. F.; McDonald, R.; Turculet, L. J. Am. Chem. Soc. 2009, 131, 14234–14236.
ꢀ
(8) Sola, E.; Garcıa-Camprubı, A.; Andres, J. L.; Martın, M.; Plou, P.
J. Am. Chem. Soc. 2010, 132, 9111–9121.
r
2010 American Chemical Society
Published on Web 10/22/2010
pubs.acs.org/IC

10650 Inorganic Chemistry, Vol. 49, No. 22, 2010
Garcıa-Camprubı et al.
disphosphines.9 Moreover, this water addition is not a dead
end, since any of its resulting fragments can undergo sub-
sequent reaction under favorable thermodynamics.
Results and Discussion
In a previous work,8 we described the behavior of the five-
coordinate complex [IrClH(biPSi)] (1). The compound forms
an equilibrium mixture of two isomers (anti and syn, attend-
ing to the relative orientation of the hydride and the methyl
substituent at silicon) that interconvert very slowly. The isomers
display rather similar structures but a noticeably different
behavior as Lewis acids. Less expectedly given its coordinative
unsaturation, we have now found that 1 also reacts with electro-
philes such as the proton, Meþ or Agþ. The final result of these
reactions is independent of the electrophile but depends on the
presence of water or hydrolizable anions, as explained below.
Reactions with Electrophiles. The simplest and clean-
est observed reactions between 1 and electrophilic re-
agents have been those with methyl triflate in chlorinated
solvents. Out of the two likely targets for the electrophile
in complex 1, the hydride or the halide ligand,10 the
methyl selectively attacks the chloride to release methyl
chloride. The in situ reaction at 250 K in CDCl3 has per-
mitted the NMR observation of the two coordina-
tion compounds resulting from this attack: tentatively for-
mulated as the syn and anti isomers of the complex
[Ir(O3SCF3)H(biPSi)] (2) (eq 1). The NMR data clearly
establish the syn or anti structure of each isomer (1H NOE)
but not the triflate coordination. Both the 19F and 13C{1H}
NMR signals corresponding to this anion are slightly shifted
with respect to those typical of non-coordinated triflates:
δ -76.71 versus -78 ppm and 119.85 versus 122 ppm,
respectively (for the major isomer 2-syn). With regard to
some precedents,11 such small chemical shift differences
might support the coordination of the triflate in 2, although
the coordination mode (chelate or monodentate) remains
unclear. Actually, this aspect could be difficult to ascertain
even with the help of X-ray data, as already discussed for the
reported complex [Ir(O2CMe)H(biPSi)], an analogue of 2
with acetate instead of triflate.8
Figure 1. Eyring representations of the rate constants for acetonitrile
dissociations from isomers 3. Activation parameters for 3-syn: trans to
silicon: ΔHq = 19 ((1) kcalmol-1, ΔSq = 27 ((1) cal K-1 mol-1; trans to
hydride: ΔHq = 25 ((1) kcal mol-1, ΔSq = 25 ((1) cal mol-1 K-1
.
For cations 3-5, this composition has been found to persist
with time and even when the acetonitrile ligands of 3 are
replaced in situ by CO or bipy. This suggests that the
observed distribution of isomers has a kinetic origin. On
the one hand, it would indicate that the reactions of 1 with
electrophiles proceed with inversion of the stereochemistry
around iridium, thus suggesting that the actions of the
electrophile and incoming ligands are somehow concerted.
On the other hand, it would imply that isomerizations (anti
to syn) are more difficult for these cationic biPSi derivatives
than for their neutral counterparts.8
Even though the clean generation of 2 is difficult and its
isolation has not been possible, a variety of its cationic
derivatives has been prepared by replacing the triflate by
other ligands: acetonitrile, carbon monoxide, and bipyr-
idine in eq 1. These cationic complexes, [IrH(biPSi)(L)2]þ
(L=NCMe (3), CO (4); L2=bipy (5)), can also be con-
veniently prepared using silver salts or HBF4 diethyl ether
solutions as electrophiles, provided these hygroscopic
reagents are dry.
Starting from equilibrium mixtures of 1(anti/syn = 83/17),8
both the neutral complex 2 and the cationic derivatives in
eq 1 have been obtained as anti/syn mixtures of approximate
composition 15/85, irrespective of the electrophilic reagent.
The easy dissociation of acetonitrile ligands in complex 3
has been subjected to a kinetic study. Pseudo-first order rate
constants (kobs) have been obtained for the exchanges
between free acetonitrile and each of the acetonitrile ligands
(9) Freixa, Z.; van Leeuwen, P. W. N. M. Coord. Chem. Rev. 2008, 252,
1755–1786.
(10) Kuhlman, R. Coord. Chem. Rev. 1997, 167, 205–232.
(11) (a) Werner, H.; Bosch, M.; Schneider, M. E.; Hahn, C.; Kukla, F.;
1
of isomers 3, using H NMR spin saturation transfer and
€
€
Manger, M.; Windmuller, B.; Webendorfer, B.; Laubender, M. J. Chem.
line-width methods (see Experimental Section). These kobs
have been found independent of the concentration of free
acetonitrile, as expected for first order dissociation pro-
cesses. The kinetic information collected for the major
isomer 3-syn, summarized in Figure 1, indicates that the
ꢀ
Soc., Dalton Trans. 1998, 3549–3558. (b) Jimenez, M. V.; Sola, E.; Martínez,
A. P.; Lahoz, F. J.; Oro, L. A. Organometallics 1999, 18, 1125–1136. (c) Jimenez,
M. V.; Sola, E.; Lopez, J. A..; Lahoz, F. J.; Oro, L. A. Chem.;Eur. J. 1998, 4,
1398–1410. (d) Goikhman, R.; Milstein, D. Angew. Chem., Int. Ed. 2001, 40,
1119–1122, and references therein.
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Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10651
generation of a coordination vacancy trans to silicon is
about 6 kcal mol-1 easier than trans to hydride, in agree-
ment with the expected trend of trans effects.12 For the
minor isomer, 3-anti, the experimental determinations could
not be extended over temperature intervals wide enough to
support Eyring analyses. Nevertheless, the rate constants
indicate that the difference in lability between the two
acetonitriles is greater for this isomer, since the ligand trans
to silicon dissociates faster than in 3-syn while than trans to
hydride does it slower.
Water. The presence of adventitious water has been
observed to modify the course of the reactions in eq 1, since
the species resulting from chloride loss, readily activate this
reagent. Again, the cleanest products have been obtained
using methyl triflate, in this case together with 1 equiv of
water. This procedure has allowed the preparation of com-
plex [Ir(O3SCF3)H2(biPSiOH)] (6) (biPSiOH = κ-O,P,P-
HOSi(Me){(CH2)3PPh2}2) in excellent yield, as a pale
yellow solid insoluble in diethyl ether (eq 2).
In spite of starting from an anti/syn mixture of 1, complex6
has been obtained as a single isomer. Its 1H NMR spectrum
shows two high-field signals corresponding to non-equivalent
hydride ligands, both doublets of triplets, with a mutual JHH
coupling constant of 8.8 Hz and clear mutual NOE effects in
the NOESY spectrum. The latter experiment also shows
the spatial proximity of the methyl substituent at silicon
and the OH hydrogen, in agreement with their proposed
syn relative orientation. Just as for complex 2, the NMR data
of 6are ambiguous when considering triflate coordination. In
fact, the 19F and 13C{1H} NMR chemical shifts of the signals
corresponding to the proposed κ-O triflate are virtually those
typical of the free anion. Yet, the in situ treatment of 6 with
acetonitrile has been observed by NMR to produce the
compound [IrH2(biPSiOH)(NCMe)](CF3SO3) (7) without
additional signals suggesting the release of water or ligands
other than triflate. This cationic complex has also been con-
veniently prepared starting from 1, water, and acetonitrile,
using triflic acid as the electrophile.
Complex 7 displays spectroscopic features similar to
those already mentioned for its neutral precursor 6 and
shows the solid state structure represented in Figure 2.
The relevant bond distances and angles of this structure
are collected in Table 1.The structure of 7 exhibits a
tridentate mer-coordinating κ-O,P,P silanol ligand con-
structed from the biPSi and the OH of a water molecule.
The silanol function displays conventional structural
Figure 2. X-ray structures of the cations of complexes 7 (above) and 8
(below).
˚
bond with the triflate anion (d(H O) = 1.957(14) A).
3 3 3
This latter interaction, very common for silanol functions
in solid state,13 has been removed from the representation
of Figure 2 for clarity, although its details are available in
the Supporting Information. As expected for a coordina-
tion position trans to hydride, the Ir-O bond distance is
˚
long, 2.254(2) A, close to the upper limit of the Ir-O bond
lengths distribution obtained from the CCDC.14 This
suggest that the silanol arm of this pincer might be readily
dissociable, a fact that would imply that the observed syn
relative orientation along the Me-Si-O-H bonds is the
thermodynamically preferred one, not a kinetic result.
The formation of Si-O bonds by silane hydrolysis or
alcoholysis has been the subject of investigation because
parameters and forms an O-H OSO2CF3 hydrogen
3 3 3
(13) Lickiss, P. D. Adv. Inorg. Chem. 1995, 42, 147–262.
(14) Allen, F. H. Acta Crystallogr. 2002, B58, 380–388.
(12) Coe, B. J.; Glenwright, S. J. Coord. Chem. Rev. 2000, 203, 5–80.

10652 Inorganic Chemistry, Vol. 49, No. 22, 2010
Garcıa-Camprubı et al.
˚
Table 1. Bond Distances (A) and Angles (deg) for Complexes 7 and 8
7
8
Ir-P(1)
Ir-P(2)
Ir-N
2.2908(9)
2.2999(9)
2.084(3)
2.3077(18)
2.3032(17)
2.245(6)
2.241(6)
2.241(4)
1.4739
1.6396
1.689(5)
155.10(6)
84.63(18)
120.66(18)
90.41(13)
68.9
Ir-C(32)
Ir-C(33)
Ir-O
2.254(2)
1.471(10)
1.471(10)
1.674(3)
171.66(3)
97.72(8)
Ir-H(2)
Ir-H(3)
Si-O
P(1)-Ir-P(2)
P(1)-Ir-N
P(1)-Ir-C(32)
P(1)-Ir-(C33)
P(1)-Ir-O
91.21(6)
83.8(12)
86.2(12)
90.60(8)
P(1)-Ir-H(2)
P(1)-Ir-H(3)
P(2)-Ir-N
82.9
P(2)-Ir-C(32)
P(2)-Ir-C(33)
120.19(18)
84.08(18)
93.37(13)
86.2
Figure 3. Hydride 1H NMR signals of complex 7 (top) and a mixture of
partially deuterated isotopomers (bottom).
P(2)-Ir-O
P(2)-Ir-H(2)
P(2)-Ir-H(3)
92.08(7)
87.9(12)
93.9(12)
93.5
C(32)-Ir-C(33)
C(32)-Ir-O
C(32)-Ir-H(2)
C(32)-Ir-H(3)
C(33)-Ir-O
C(33)-Ir-H(2)
C(33)-Ir-H(3)
36.1(2)
85.5(2)
153.0
provoking the fast redistribution of the label among all these
acidic sites. The experiments have confirmed the thermody-
namic preference of 2H for the silanol position and its similar
affinity for both hydride sites. Figure 3 illustrates the shift
provoked by the 2H isotopic substitution at the hydride site in
the 1H NMR signal of the neighboring hydride. In addition,
each hydride isotopic substitution has been found to shift the
31P{1H} NMR signal of the complex by þ0.10 ppm. These
isotopic shifts are of the same sign and magnitude as those
previously observed in related Ir(III) compounds.19
N-Ir-O
N-Ir-H(2)
N-Ir-H(3)
87.48(10)
176.6(13)
93.9(14)
92.2
88.3(2)
167.9
93.6
99.5
173.1
79.7
O-Ir-H(2)
O-Ir-H(3)
H(2)-Ir-H(3)
95.6(13)
177.2(12)
83.1(18)
of the importance of silanols as bulding blocks in organic
synthesis and in the polymer industry,13 and because of the
generalized use of silyl ethers as protecting groups for the
hydroxyl function.15 These reactions can be catalyzed by a
variety of soluble metal complexes,16 some of them of
iridium.17 The prevalent mechanistic description for Si-O
bond formation during such processes involves the nucleo-
philic attack of water or alcohol to a previously activated
silane at the metal coordination sphere,16,17 a step fully
consistent with the reaction in eq 2. The closest precedent
for this reaction was described for the coordinatively satu-
rated ruthenium complex [RuH(biPSi)(CO)2], which was
found capable of incorporating the oxygen atom of water,
in the presence of bases, to form κ-O,P,P siloxide com-
plexes.18 In that system, the use of isotopically labeled water
confirmed the source of oxygen atoms but did not offer
further mechanistic information about the water splitting
process. Our experiments using 2H-labeled water in eq 2 have
also failed to extract mechanistic information because of the
Brønsted acidity of both the silanol and the hydrides of
products 6 and 7. These three hydrogen atoms have been
found to rapidly exchange with the protons of free water
As expected from its long Ir-N bond distance,
2.084(3) A,20 the acetonitrile ligand of complex 7 can be
˚
readily substituted by a variety of other ligands. Equation 3
depicts the substitution by ethylene, which has led to the
dihydride-ethylene complex [IrH2(biPSiOH)(η2-C2H4)]-
(CF3SO3) (8). The NMR spectroscopic observation of the
reaction has confirmed that acetonitrile substitution is
nearly immediate, while the possible replacement of the
silanol arm of the pincer has not been detected with a
moderate excess of ethylene (e.g., CDCl3 saturated solu-
tions at room temperature).
(15) Kocienski, P. J. Protecting Groups; Thieme: Stuttgart, 1994; pp 28-42.
(16) (a) Chang, S.; Scharrer, E.; Brookhart, M. J. Mol. Catal. A 1998, 130,
107–119. (b) B€uhl, M.; Mauschick, F. T. Organometallics 2003, 22, 1422–1431.
(c) Corbin, R. A.; Ison, E. A.; Abu-Omar, M. M. Dalton Trans. 2009, 2850–2855.
(d) Peterson, E.; Khalimon, A. Y.; Simionescu, R.; Kuzmina, L. G.; Howard,
J. A. K.; Nikonov, G. I. J. Am. Chem. Soc. 2009, 131, 908–909. (e) Matthews,
S. L.; Pons, V.; Heinekey, M. Inorg. Chem. 2006, 45, 6453–6459. (f) Fang, X.;
Huhmann-Vincent, J.; Scott, B. L.; Kubas, G. J. J. Organomet. Chem. 2000, 609,
95–103.
(17) (a) Luo, X.-L.; Crabtree, R. H. J. Am. Chem. Soc. 1989, 111, 2527–
2535. (b) Field, L. D.; Messerle, B. A.; Rehr, M.; Soler, L. P.; Hambley, T. W.
Organometallics 2003, 22, 2387–2395. (c) Lee, Y.; Seomoon, D.; Kim, S.; Han,
H.; Chang, S.; Lee, P. H. J. Org. Chem. 2004, 69, 1741–1743. (d) Calimano, E.;
Tilley, T. D. Organometallics 2010, 29, 1680–1692.
ꢀ
(19) For examples, see: (a) Sola, E.; Navarro, J.; Lopez, J. A.; Lahoz, F. J.;
Oro, L. A.; Werner, H. Organometallics 1999, 18, 3534–3546. (b) Navarro, J.;
Sola, E.; Martín, M.; Dobrinovitch, I. T.; Lahoz, F. J.; Oro, L. A. Organometallics
2004, 23, 1908–1917. (c) Sola, E.; Bakhmutov, V. I.; Torres, F.; Elduque, A.;
ꢀ
Lopez, J. A.; Lahoz, F. J.; Werner, H.; Oro, L. A. Organometallics 1998, 17,
683–696.
(20) For values of this bond distance in related labile complexes see
references 19a, 19b, and (a) Torres, O.; Martın, M.; Sola, E. Organometallics
2009, 28, 863–870. (b) Torres, O.; Martín, M.; Sola, E. Organometallics 2010,
29, 3201–3209.
(18) Stobart, S. R.; Zhou, X.; Cea-Olivares, R.; Toscazo, A. Organo-
metallics 2001, 20, 4766–4768.

Article
The X-ray structure of the cation of complex 8 is shown
Inorganic Chemistry, Vol. 49, No. 22, 2010 10653
15.6 Hz present in both alkenyl hydrogen 1H NMR
signals. The mutually cis hydride and alkenyl ligands
have not been seen to undergo spontaneous reductive
elimination in solution. Nevertheless, the complex has
been found to slowly decompose when heating to form
several species that could not be identified.
in Figure 2. Its main bond distances and angles are
collected in Table 1. The structure shows various similar-
ities with that of its precursor 7, including a hydrogen
bond with the triflate anion (also removed for clarity in
˚
Figure 2, H O distance 1.92(7) A). The most note-
3 3 3
Hydrolyzable Fluorinated Anions. If, besides water, the
reactions of 1 with electrophiles contain anions suscep-
tible to hydrolysis, such as hexafluorophosphate or
tetrafluoroborate,24 the final products are not those of
eq 2 but species that incorporate fluoride at the silicon
atom of the former biPSi ligand (eq 4). The treatment of 1
with 2 equiv of a wet diethyl ether solution of HBF4 in the
presence of acetonitrile has led to the cationic dihydride
complex [IrH2(biPSiF)(NCMe)2]BF4 (11) (biPSiF =
κ-P2-FSi(Me){(CH2)3PPh2}2). The compound has also
been prepared from 7 and acetonitrile, via treatment with
sodium fluoride or sodium tetrafluoroborate. Along this
latter reaction, the 19F NMR spectra have confirmed the
formation of BF4- hydrolysis byproducts (BF3(OH) -, etc.).
worthy structural detail of 8 concerns the orientation of
the ethylene ligand, almost parallel to the P-Ir-P axis.
This orientation does not seem the sterically preferred
one, as it causes a clear distortion in the angle between
the two phosphorus atoms, from 172° in 7 to 155° in 8.
More likely, according to the Chatt-Dewar-Duncanson
bonding model,21 the observed orientation is that maxi-
mizing the back-bonding from metal filled orbitals to the
π* olefin orbital. The magnitude of this bond contribu-
tion seems to be significant because the elongation of the
˚
CdC bond is notable (1.391(4) vs 1.339 A in free
ethylene)22 in spite of the unusually long Ir-C distances
(2.245(6) and 2.241(6) A).14,23 The 1H NMR spectrum of
˚
8 at room temperature displays a single signal attributable
to the ethylene ligand, a poorly resolved multiplet at δ
2.66 containing a JHP coupling constant of about 2.1 Hz.
The VT NMR spectra in CD2Cl2 have not shown any
significant broadening of this signal above 213 K, nor its
decoalescence at the lowest temperature attained, 183 K.
This behavior is consistent with a low barrier for ethylene
rotation.
Insertion of the ethylene ligand into the neighboring
Ir-H is a very slow process. In the presence of aceto-
nitrile, this insertion has been found to afford the ethyl-
hydride complex [Ir(Et)H(biPSiOH)(NCMe)](CF3SO3)
(9). As shown in eq 3, this latter complex is the stable
product of the reaction between 7 and ethylene, whereas
the above-described dihydride-ethylene complex 8 is just
an intermediate. Yet, the formation of 9 is so slow that it
has not caused any problem in the characterization of 8 or
its crystallization. In fact, the complete formation of 9 has
not been observed, so that its characterization was ac-
complished in solution by NMR once it became the major
product in the reaction mixture, after approximately
1
2 weeks of reaction at room temperature. The H and
13C{1H} NMR spectra of 9 display characteristic reso-
nances for the ethyl ligand, and the 1H NOESY spectrum
reveals the cis position of this ligand relative to the
hydride.
A second insertion product, analogous to 9, has been
obtained after the treatment of 7 with phenylacetylene
(eq 3). This alkyne insertion is also relatively slow,
although it has been completed in a few hours at room
temperature. The reaction product, [Ir(E-CHdCHPh)H-
(biPSiOH)(NCMe)](CF3SO3) (10), has been isolated and
characterized as a single isomer containing an E alkenyl
ligand, as indicated by the JHH coupling constant of
Most likely, this reaction is thermodynamically driven
by the formation of the very strong Si-F bond (above
150 kcal mol-1). Evidence for this new bond is provided
by the NMR spectra of 11, in the form of a JSiF coupling
constant of 287.6 Hz in the 29Si{1H} spectrum (Figure 4),
a new signal at δ -167.02 in the 19F spectrum displaying
29Si satellites, and a JCF coupling constant of 14.1 Hz in
the 13C{1H} NMR signal corresponding to the methyl
substituent at silicon. The NMR spectra also indicate the
equivalence of the phosphorus atoms and non-equiva-
lence of acetonitriles and hydrides. The 1H NMR signals
of the latter show a JHH mutual coupling constant of
6.3 Hz, in agreement with their cis relative position. This
structural information implies that the new diphosphine
generated after silicon fluorination coordinates via two
€
(21) Frenking, G.; Frohlich, N. Chem. Rev. 2000, 100, 717–774.
(22) Lide, D. R. Handbook of Chemistry and Physics, 76th ed.; CRC Press
Inc.: Boca Raton, FL, 1996.
ꢀ
(23) For examples ofIr(III) ethylene complexes: (a) Lara,P.; Lopez-Serrano,
ꢀ
J.; Maya, C.; Paneque, M.; Poveda, M. L.; Sanchez, L. J.; Valpuesta, J. E. V.;
Carmona, E. Organometallics 2009, 28, 4649–4651. (b) Young, K. J. H.; Oxgaard,
J.; Ess, D. H.; Meier, S. K.; Stewart, T.; Goddard, W. A., III; Periana, R. A. Chem.
Commun. 2009, 3270–3272. (c) Paredes, P.; Díez, J.; Gamasa, M. P. Organo-
metallics 2008, 27, 2597–2607. (d) Burger, P.; Bergman, R. G. J. Am. Chem. Soc.
1993, 115, 10462–10463. (e) Lundquist, E. G.; Folting, K.; Huffman, J. C.; Caulton,
K. G. Organometallics 1990, 9, 2254–2261.
(24) (a) Wamser, C. A. J. Am. Chem. Soc. 1948, 70, 1209–1215. (b) Mesmer,
R. E.; Palen, K. M.; Baes, C. F., Jr. Inorg. Chem. 1973, 12, 89–95.
ꢀ
ꢀ
(c) Fernandez-Galan, R.; Manzano, B. R.; Otero, A.; Lanfranchi, M.; Pellinghelli,
M. A. Inorg. Chem. 1994, 33, 2309–2312, and references therein.

10654 Inorganic Chemistry, Vol. 49, No. 22, 2010
Garcıa-Camprubı et al.
˚
Table 2. Bond Distances (A) and Angles (deg) for Complex 12
Ir-P(1)
2.3108(16)
2.3233(18)
2.064(5)
Ir-P(2)
Ir-C(3)
Ir-N(2)
2.3541(17)
2.097(6)
2.155(5)
Ir-Si
Ir-N(1)
P(1)-Ir-P(2)
P(1)-Ir-Si
P(1)-Ir-C(3)
P(1)-Ir-N(1)
P(1)-Ir-N(2)
Si-Ir-N(1)
C-Ir-N(1)
Si-Ir-C
170.51(6)
88.44(6)
P(2)-Ir-Si
93.02(6)
87.54(18)
93.10(14)
89.59(14)
176.17(14)
88.1(2)
83.10(18)
96.17(14)
88.53(14)
93.63(15)
177.1(2)
P(2)-Ir-C(3)
P(2)-Ir-N(1)
P(2)-Ir-N(2)
Si-Ir-N(2)
C-Ir-N(2)
89.20(19)
N(1)-Ir-N(2)
89.0(2)
Figure 5; its main bond distances and angles are collected in
Table 2. The slow development of this complex at room
temperature has been monitored by NMR in CDCl3 solu-
tions of 11, from which it has been crystallized in low yield.
Mechanistically, the formation of 12 from 11 can be ratio-
nalized in two steps, namely, H2 loss and Si-C bond
activation; most likely in that order. An example of the
second step has recently been reported for Ni(0) and Pd(0)
species with closely related κ-P,P,Si pincer ligands.27 Given
the difficulties inherent for the reductive elimination of H2
from Ir(III) dihydrides,28 this step is most likely rate limiting
in the formation of 12. This mechanistic rationalization has
been implemented by introducing a hydrogen acceptor such
as ethylene in the reaction (eq 4), which has rendered
reaction times of a few hours instead of weeks. Nevertheless,
this procedure seems to favor the formation of several
byproducts that could not be conveniently separated from 12.
The monitoring of this reaction by NMR has shown the
formation of several dihydride and monohydride reaction
intermediates, probably in route to Ir(I) species, although
they have not been investigated in more detail.
Figure 4. 29Si{1H} NMR spectra of complexes 1-anti, 7, and 11.
Conclusion
The simple reactions and mild conditions necessary to trans-
form the complex [IrClH(biPSi)] (1) into radically different
derivatives such as 11 and 12 highlight that, despite its integra-
tion into a polydentate ligand, the silicon atom of the biPSi
remains a reactive site. The sequence of reactions unraveled
throughout this study most likely starts at the labile Ir(III)
coordination sphere generated after the removal of chloride by
an electrophile, and is driven by the strength of single bonds
such as Si-O or Si-F. These reactions indicate that certain
experimental conditions should be avoided when searching for
catalytic applications of 1 and related species. Nevertheless,
each of these reactions constitutes a route for the transforma-
tion of 1 into a new type of complex with potential application
in catalysis. These include cationic dihydride-solvato complexes
containing either silanol pincers or trans-chelating diphosphines
generated from the silanol templates. In particular, compounds
such as 7and 8, which incorporate the H and OH fragments of a
split water molecule and offer readily accessible coordination
sites, merit further examination within the contexts of hydrogen
production and catalytic hydration.
Figure 5. X-ray structure of the cation of complex 12.
mutually trans positions of an assumed octahedron.
Although relatively unusual, such trans-chelating coordi-
nation is known for diphosphines9 and other ligands25
with long chains connecting the donor atoms. Apart from
the backbone connecting the two phosphorus, the coor-
dination sphere of iridium in 11 is that of the known
complex [IrH2(PR3)2(NCMe)2]BF4.26
The attempts to confirm the proposed structure of 11
by X-ray diffraction have led to the characterization of a
derivative, the complex [Ir{κ-P,Si-Si(F)(Me)CH2CH2-
CH2PPh2}(κ-C,P-CH2CH2CH2PPh2)(NCMe)2]BF4 (12).
One of the enantiomers of this compound is shown in
Experimental Section
Equipment. C, H, and N analyses were carried out in a Perkin-
Elmer 2400 CHNS/O analyzer. Matrix-assisted laser desorption/
ionization-time-of-flight mass spectrometry (MALDI-TOF-MS)
(25) Skopek, K.; Hershberger, M. C.; Gladysz, J. A. Coord. Chem. Rev.
2007, 251, 1723–1733.
(26) He, X. D.; Fernandez-Baeza, J.; Chaudret, B.; Felting, K.; Caulton,
K. G. Inorg. Chem. 1990, 29, 5000–5002.
(27) Mitton, S. J.; McDonald, R.; Turculet, L. Angew. Chem., Int. Ed.
2009, 48, 8568–8571.
(28) Dobereiner, G. E.; Crabtree, R. H. Chem. Rev. 2010, 110, 681–703.

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10655
data were obtained in a Bruker Microflex mass spectrometer
using DIT (1,8,9-trihydroxy-anthracene) as matrix. Infrared
spectra were recorded in KBr using a FTIR Perkin-Elmer Spec-
trum One spectrometer. NMR spectra were recorded on Bruker
Avance 400 or 300 MHz spectrometers. 1H (400.13 or 300.13 MHz)
and 13C (100.6 or 75.5 MHz) NMR chemical shifts were mea-
sured relative to partially deuterated solvent peaks but are reported
in parts per million (ppm) relative to TMS. 19F (376.5 or 288.3
MHz), 31P (162.0 or 121.5 MHz), and 29Si (59.6 or 79.5 MHz)
NMR chemical shifts were measured relative to CFCl3, H3PO4
(85%), and TMS, respectively. In general, NMR spectral assign-
ments were achieved through 1H COSY, 1H NOESY, 13C APT,
J
CP = 23.2, C), 134.21 (t, JCP=5.6, CH), 131.16 (t, JCP=5.0,
CH), 131.0, 129.87 (both s, CH), 128.76 (t, JCP = 4.5, CH),
128.58 (t, JCP = 5.1, CH), 121.02 (s, NCCH3), 27.37 (t, JCP
18.2, PCH2), 19.81 (s, CH2), 15.42 (t, JCP = 5.4, CH2), 3.47 (s,
NCCH3), 2.82 (s, CH3).
=
Preparation of [IrH(biPSi)(CO)2]PF6 (4). A 5 mL CH2Cl2
solution of 3 (80 mg, 0.08 mmol) was stirred under a CO
atmosphere (ca. 1 bar) for 15 min at room temperature. The
resulting solution was concentrated to about 0.5 mL and treated
with diethyl ether to give a pale yellow solid. The solid was
separated by decantation, washed with diethyl ether, and dried:
yield 59 mg (83%). Anal. Calcd (%) for C33H36F6IrO2P3Si: C,
1
and H/13C-HSQC experiments. Spectroscopic data are given at
44.44; H, 4.07. Found: C, 44.75; H, 4.02. MS (m/z): 719 [Mþ
-
CO]. IR (cm-1): 2091, 2033 ν(CO). Partial data for 4-anti: H
NMR (CDCl3): δ 8.16-7.4 (m, 20H, Ph), 3.16, 2.81, 2.48, 1.90,
1.32, 0.93 (all m, 2H each, CH2), 0.53 (s, 3H, CH3), -9.03 (t,
JHP = 14.5, 1H, IrH). 31P{1H} NMR (CDCl3): δ -22.51 (s).
13C{1H} NMR (CDCl3): δ 131.33, 130.78 (both t, JCP = 5.2,
CH), 132.32, 131.75 (both s, CH), 129.54 (t, JCP = 5.5, CH),
129.41 (t, JCP = 5.4, CH), 28.45 (t, JCP = 21.1, PCH2), 18.93
(s, CH2), 15.09 (t, JCP = 5.7, CH2), 3.93 (s, CH3). Partial data for
4-syn: 1H NMR (CDCl3): δ 8.16-7.4 (m, 20H, Ph), 3.38, 2.89,
2.69, 1.95, 1.43, 1.02 (all m, 2H each, CH2), 0.34 (s, 3H, CH3),
-8.74 (t, JHP = 12.5, 1H, IrH). 31P{1H} NMR (CDCl3): δ
-23.20 (s). 13C{1H} NMR (CDCl3): δ 171.64 (t, JCP = 5.8, CO),
161.06 (t, JCP = 8.2, CO), 136.41 (t, JCP = 28.5, C), 133.70 (t,
JCP = 6.0, CH), 132.13 (t, JCP = 6.0, CH), 133.02, 131.75 (both
s, CH), 129.91 (t, JCP = 5.5, CH), 129.76 (t, JCP = 5.0, CH),
126.05 (t, JCP = 32.4, C), 28.77 (t, JCP = 19.8, PCH2), 19.15 (s,
CH2), 15.92 (t, JCP = 4.6, CH2), 4.05 (s, CH3).
1
room temperature unless otherwise indicated.
Synthesis. All manipulations were carried out under argon by
standard Schlenk techniques. Solvents were obtained from an
Innovative Technology solvent purification system. Deuterated
solvents were dried with appropriate drying agents and degassed
with argon prior to use. The starting complex [IrClH(biPSi)] (1)
was prepared by known procedures.29 All commercial reagents
were used as received without further purification. All new
complexes described below are air sensitive in solution.
[Ir(O3SCF3)H(biPSi)] (2). To a 0.5 mL CDCl3 solution of 1
(25.0 mg, 0.03 mmol) in a NMR tube was added methyl triflate
(3.9 μL, 0.03 mmol). The resulting mixture was cooled down to
253 K and analyzed by NMR. Methyl chloride, and the anti and
syn isomers of 2 in relative proportion 15:85, respectively, were
the only detectable reaction products. Partial data for 2-anti: 1H
NMR (CDCl3, 253 K): δ -28.25 (t, JHP = 16.0, 1H, IrH).
31P{1H} NMR (CDCl3, 253 K): δ 14.90 (s). Partial data for
2-syn: 1H NMR (CDCl3, 253 K): δ 7.95 (m, 4H, CH), 7.58 (m,
8H, CH), 7.25 (m, 8H, CH), 3.36, 2.86, 2.19, 1.54, 1.43, 0.60 (all
m, 2H each, CH2), -0.10 (s, 3H, CH3), -27.19 (t, JHP = 12.6,
1H, IrH). 31P{1H} NMR (CDCl3, 253 K): δ 13.88 (s). 19F NMR
(CDCl3, 253 K): δ -76.71 (s). 13C{1H} NMR (CDCl3, 253 K): δ
134.75, 132.58 (both t, JCP = 6.1, CH), 129.99, 129.71 (both s,
Preparation of [IrH(biPSi)(K2-N-bipy)]PF6 (5). To a 5 mL
CH2Cl2 solution of 3 (100 mg, 0.11 mmol) was added 2,20-
bipyridine (16 mg, 0.11 mmol). The reaction mixture was stirred
at room temperature for 15 min, after which it was concentrated
to about 0.5 mL. The addition of diethyl ether produced a pale
yellow solid, which was separated by decantation, washed with
diethyl ether, and dried: yield 81 mg (81%). Anal. Calcd (%) for
C41H44F6IrN2P3Si: C, 49.64; H, 4.47; N, 2.82. Found: C, 49.74;
H, 4.34; N, 2.63. Partial data for 5-anti: 1H NMR (acetone-d6): δ
0.13 (s, 3H, CH3), -19.60 (t, JHP = 13.1, 1H, IrH). 31P{1H}
NMR (acetone-d6): δ -5.00 (s). Partial data for 25-syn: 1H
NMR (acetone-d6): δ 9.59(d, JHH = 5.3, 2H, CH), 8.87(d,
JHH = 5.0, 2H, CH), 8.30 (m, 6H, CH), 8.03 (td, JHH = 1.3,
5.5, 2H, CH), 7.52 (d, JHH = 1.2, 6.8, 2H, CH), 7.54 (m, 6H,
CH), 7.34, 7.19 (both m, 4H, CH), 2.71, 2.51, 2.27, 1.54, 1.57,
CH), 128.29, 127.99 (both t, JCP = 5.4, CH), 119.85 (q, JCF =
318.9, CF3), 28.87 (t, JCP = 16.9, PCH2), 18.30, 17.62 (both s,
CH2), 6.38 (s, CH3).
Preparation of [IrH(biPSi)(NCMe)2]PF6 (3). To a 5 mL
acetone solution of 1 (148 mg, 0.20 mmol) were added aceto-
nitrile (31 μL, 0.60 mmol) and silver hexafluorophosphate (51 mg,
0.20 mmol). The mixture was protected from the daylight and
stirred for 45 min, after which it was filtered through Celite to
remove the insoluble silver chloride. The resulting solution was
concentrated to about 0.5 mL and treated with diethyl ether to
give a white solid. The solid was separated by decantation,
washed with diethyl ether, and dried in vacuo: yield 130 mg
(71%). Anal. Calcd (%) for C35H42N2F6IrP3Si: C, 45.79; H,
4.61; N, 3.05. Found: C, 46.21; H, 4.74; N, 2.72. IR (cm-1):
2250 ν(IrH). Partial data for 3-anti: 1H NMR (CDCl3): δ 7.98
(m, 4H, CH), 7.45 (m, 16H, CH), 2.91, 2.75 (both m, 2H each,
CH2), 2.46 (s, 3H, NCCH3), 2.43, 1.79 (both m, 2H each, CH2),
1.47 (s, 3H, NCCH3), 0.79, 0.67 (both m, 2H each, CH2), -0.26
(s, 3H, CH3), -18.83 (t, JHP = 15.2, 1H, IrH). 31P{1H} NMR
(CDCl3): δ -5.28 (s). 13C{1H} NMR (CDCl3): δ 135.18 (t,
0.79 (all m, 2H each, CH2), 0.32 (s, 3H, CH3),-18.90 (t, JHP
=
12.8, 1H, IrH). 31P{1H} NMR (acetone-d6): δ -2.00 (s). 13C{1H}
NMR (acetone-d6): δ 158.27(s, C), 155.42, 139.33 (both s, CH),
135.91 (t, JCP = 6.3, CH), 132.43 (s, CH), 129.86 (t, JCP = 4.3,
CH), 129.75 (t, JCP = 5.3, CH), 129.29 (s, CH), 128.56 (t, JCP =
4, CH), 124.55, 121.83 (both s, CH), 27.24 (t, JCP = 18.6, PCH2),
20.53 (s, CH2), 17.41 (t, JCP = 4.2, CH2), 8.64 (s, CH3).
Preparation of [Ir(O3SCF3)H2(biPSiOH)] (6). To a 5 mL
CH2Cl2 solution of 1 (125 mg, 0.17 mmol) were added water
(3.5 μL, 0.2 mmol) and methyl triflate (19 μL, 0.17 mmol). The
reaction mixture was stirred at room temperature for 15 min,
after which it was concentrated to about 0.5 mL. The addition of
diethyl ether produced a pale yellow solid, which was separated
by decantation, washed with diethyl ether, and dried: yield
168 mg (98%). Anal. Calcd (%) for C32H38F3IrO4P2SSi: C,
44.80; H, 4.46; S, 3.74. Found: C, 44.97; H, 4.80; S, 3.76. MS (m/
z): 707 [Mþ - O3SCF3 - 2H]. 1H NMR (CDCl3): δ 7.89 (m, 4H,
CH), 7.47 (m, 6H, CH), 7.27 (m, 2H, CH), 7.14 (m, 6H, CH),
7.05 (m, 2H, CH), 6.76 (s, 1H, OH), 2.94, 2.56, 1.89, 1.56, 1.14,
JCP = 27.1, C), 132.93 (t, JCP = 5.8, CH), 132.38 (t, JCP
4.9, CH), 130.47, 130.02 (both s, CH), 128.84 (t, JCP = 4.2, CH),
128.17 (t, JCP = 5.1, CH), 120.93 (s, NCCH3), 30.75 (t, JCP
=
=
19.7, PCH2), 22.64 (s, CH2), 17.84 (t, JCP=3.9, CH2), 3.28 (s,
NCCH3), 0.75 (s, CH3). Partial data for 3-syn: 1H NMR
(CDCl3): δ 7.98 (m, 4H, CH), 7.45 (m, 16H, CH), 2.91, 2.75
(both m, 2H each, CH2), 2.56 (s, 3H, NCCH3), 2.43, 1.79 (both
m, 2H each, CH2), 0.79, 0.67 (both m, 2H each, CH2), -0.11
(s, 3H, CH3), -19.41 (t, JHP = 14.0, 1H, IrH). 31P{1H} NMR
(CDCl3): δ -3.28 (s). 13C{1H} NMR (CDCl3): δ 134.56 (t,
0.52 (all m, 2H each, CH2), 0.47 (s, 3H, CH3), -27.31 (td, JHP
=
16.0, JHH = 8.8, 1H, IrH), -29.09 (td, JHP = 14.4, JHH = 8.8,
1H, IrH). 31P{1H} NMR (CDCl3): δ 23.34 (s). 19F NMR
(CDCl3): δ -77.98 (s). 13C{1H} NMR (CDCl3): δ 135.62 (t,
(29) Stobart, S. R.; Brost, R. D.; Bruce, G. C.; Joslin, F. L. Organo-
metallics 1997, 16, 5669–5680.
JCP = 6.5, CH), 135.36 (t, JCP = 17.2, C), 131.27 (s, CH), 131.09

10656 Inorganic Chemistry, Vol. 49, No. 22, 2010
Garcıa-Camprubı et al.
(t, JCP = 5.1, CH), 130.97 (t, JCP = 29.6, C), 129.06 (s, CH),
128.63 (t, JCP = 5.3, CH), 128.32 (t, JCP = 4.0, CH), 122.29 (q,
JCF = 318.3, CF3), 24.88 (t, JCP = 15.1, PCH2), 17.41, 16.39
(both s, CH2), -2.02 (s, CH3). 29Si{1H} NMR (CDCl3): δ 22.74 (s).
Preparation of [IrH2(biPSiOH)(NCMe)](CF3SO3) (7). To a
5 mL CH2Cl2 solution of 1 (312 mg, 0.43 mmol) were sequentially
added water (8 μL, 0.44 mmol), triflic acid (38 μL, 0.43 mmol),
and acetonitrile (30 μL, 0.58 mmol). The resulting solution was
stirred at room temperature for 15 min, after which it was
concentrated to about 0.5 mL. The addition of diethyl ether
produced a pale yellow solid, which was separated by decanta-
tion, washed with diethyl ether, and dried: yield 371 mg (93%).
Anal. Calcd (%) for C34H41NF3IrO4P2SSi: C, 45.42; H, 4.60; N,
1.56; S, 3.57. Found: C, 45.09; H, 4.65; N, 2.04; S, 3.29. MS
(m/z): 748 [Mþ - H2]. IR (cm-1): 2204 ν(IrH). 1H NMR
(CDCl3): δ 8.07 (m, 2H, CH), 7.44 (m, 18H, CH), 6.72 (s, 1H,
OH), 2.96, 2.77, 2.05, 1.75 (all m, 2H each, CH2), 1.56 (s, 3H,
NCCH3), 1.33, 0.65 (both m, 2H each, CH2), 0.55 (s, 3H, CH3),
Preparation of [Ir(E-CHdCHPh)H(biPSiOH)(NCMe)]-
(CF3SO3) (10). To a 5 mL CH2Cl2 solution of 7 (180 mg, 0.20
mmol) was added phenylacetylene (33 μL, 0.30 mmol). The
resulting solution was stirred at room temperature for 48 h and
concentrated to about 0.5 mL. The addition of diethyl ether
produced a yellow solid, which was separated by decantation,
washed with diethyl ether, and dried: yield 156 mg (78%). Anal.
Calcd (%) for C42H47NF3IrO4P2SSi: C, 50.39; H, 4.73; N, 1.40;
1
S, 3.20. Found: C, 50.70; H, 4.91; N, 1.35; S, 3.36. H NMR
(CDCl3): δ 7.8-6.8 (m, 20H, CH), 7.76 (brd, JHH = 15.6, 1H,
IrCHCHPh), 6.48 (s, 1H, OH), 5.28 (d, JHH = 15.6, 1H,
IrCHCHPh), 2.85, 2.29, 1.84, 1.53 (all m, 2H each, CH2), 1.49
(s, 3H, NCCH3), 1.27, 0.45 (both m, 2H each, CH2), 0.38 (s, 3H,
CH3), -18.53 (t, JHP = 14.0, 1H, IrH). 31P{1H} NMR (CDCl3):
δ 11.99 (s). 19F NMR (CDCl3): δ -80.33 (s). 13C{1H} NMR
(CDCl3): δ 134.53 (t, JCP = 6.0, CH), 132.91 (s, IrCCH), 132.76
(t, JCP = 23.4, C), 131.78 (t, JCP = 4.7, CH), 130.94, 129.30
(both s, CH), 128.60 (t, JCP = 5.1, CH), 127.29 (t, JCP = 4.2,
CH), 122.29 (q, JCF = 320.0, CF3), 117.96 (br, NCCH3), 106.66
(t, JCP = 9.3, IrCH), 25.85 (t, JCP = 15.9, PCH2), 17.03, 15.17
(both s, CH2), 2.41 (s, NCCH3), -2.59 (s, CH3). 29Si{1H} NMR
(CDCl3): δ 24.66 (s).
-19.81 (td, JHP = 16.0, JHH = 7.4, 1H, IrH), -28.75 (td, JHP
=
13.8, JHH = 7.4, 1H, IrH). 31P{1H} NMR (CDCl3): δ 18.56 (s).
19F NMR (CDCl3): δ -78.11 (s). 13C{1H} NMR (CDCl3,): δ
135.54 (t, JCP = 22.9, C), 135.39 (t, JCP = 6.5, CH), 131.59 (t,
JCP = 28.9, C), 131.13 (t, JCP = 5.2, CH), 128.74, 128.70 (both s,
CH), 128.45 (t, JCP = 5.3, CH), 122.35 (q, JCF = 319.9, CF3),
118.90 (s, NCCH3), 25.10 (t, JCP = 15.4, CH2), 17.19, 16.21
(both s, CH2), 2.36 (s, NCCH3), -2.09 (s, CH3). 29Si{1H} NMR
(CDCl3): δ 22.99 (s). The crystals used in the X-ray experiment
were obtained from a CH2Cl2 solution layered with diethyl
ether, at room temperature.
Preparation of [IrH2(biPSiF)(NCMe)2]BF4 (11). To a 5 mL
CH2Cl2 solution of 1 (100 mg, 0.14 mmol) were sequentially
added water (3 μL, 0.17 mmol), tetrafluoroboric acid diethyl
ether complex (41 μL, 0.30 mmol), and acetonitrile (15 μL,
0.29 mmol). The resulting solution was stirred at room tem-
perature for 30 min, after which it was concentrated to about
0.5 mL. The addition of diethyl ether produced a pale yellow
solid, which was separated by decantation, washed with diethyl
ether, and dried: yield 94 mg (76%). Anal. Calcd (%) for
C35H43N2BF5IrP2Si: C, 47.78; H, 4.93; N, 3.18. Found: C,
47.55; H, 4.90; N, 2.98. MS (m/z): 709 [Mþ - 2H - 2NCMe].
Preparation of [IrH2(biPSiOH)(η2-C2H4)](CF3SO3) (8). A
5 mL CH2Cl2 solution of 7 (101 mg, 0.11 mmol) was stirred under
ethylene atmosphere (ca. 1 bar) for 15 min at room temperature.
The resulting solution was concentrated to about 0.5 mL and
treated with diethyl ether to give a pale yellow solid. The solid
was separated by decantation, washed with diethyl ether, and
dried: yield 88 mg (90%). Anal. Calcd (%) for C34H42F3Ir-
O4P2SSi: C, 46.09; H, 4.78; S, 3.62. Found: C, 45.93; H, 5.02; S,
1
IR (cm-1): 2197 ν(IrH). H NMR (CDCl3): δ 7.48 (m, 20H,
CH), 2.54 (m, 4H, CH2), 1.87, 1.70 (both s, 3H each, NCCH3),
1.69, 1.08 (both m, 4H each, CH2), 1.65 (d, JHF = 7.5, 3H, CH3),
-21.12 (td, JHP = 16.8, JHH = 6.3, 1H, IrH), -21.38 (td, JHP
=
17.7, JHH = 6.3, 1H, IrH). 31P{1H} NMR (CDCl3): δ 9.92 (s).
=
1
3.46. IR (cm-1): 2232, 2176 ν(IrH). H NMR (CDCl3): δ 7.88
19F NMR (CDCl3): δ -155.08 (br, BF4), -167.02 (m, JFH
(m, 2H, CH), 7.45 (m, 8H, CH), 7.27 (m, 2H, CH), 7.18 (m, 8H,
CH), 5.68 (s, 1H, OH), 2.78 (m, 4H, CH2), 2.66 (m, 4H, C2H4),
1.94, 1.51, 0.97, 0.43 (all m, 2H each, CH2), 0.30 (s, 3H, CH3),
7.5, SiF). 13C{1H} NMR (CDCl3): δ 133.05 (t, JCP = 23.7, C),
132.79 (t, JCP = 6.0, CH), 132.45 (t, JCP = 5.7, CH), 130.41,
130.24 (both s, CH), 128.58 (t, JCP = 4.7 CH), 128.55 (t, JCP =
-9.64 (td, JHP = 16.8, JHH = 6.4, 1H, IrH), -30.68 (td, JHP
=
13.6, JHH = 6.4, 1H, IrH). 31P{1H} NMR (CDCl3): δ 11.73 (s).
19F NMR (CDCl3): δ -78.05 (s). 13C{1H} NMR (CDCl3):
δ 136.28 (t, JCP = 26.3, C), 134.94 (t, JCP = 6.0, CH), 132.25
(t, JCP = 31.1, C), 129.63 (s, CH), 130.53 (t, JCP = 4.6, CH),
129.63 (s, CH), 128.48 (t, JCP = 5.3, CH), 128.33 (t, JCP = 4.5,
CH), 122.01 (q, JCF = 319.5, CF3), 65.81 (s, C2H4), 24.42 (t, JCP
= 15.9, PCH2), 16.97, 15.24 (both s, CH2), -2.49 (s, CH3).
29Si{1H} NMR (CDCl3): δ 24.91 (s). The crystals used in the
X-ray experiment were obtained from a CH2Cl2 solution layered
with diethyl ether, at room temperature.
4.7, CH), 120.14, 119.56 (both s, NCCH3), 34.81 (t, JCP = 20.3,
PCH2), 17.17 (s, CH2), 16.54 (dt, JCF = 13.2, JCP = 3.3, CH2),
2.43, 2.24 (both s, NCCH3), -1.97 (d, JCF = 14.1, CH3).
29Si{1H} NMR (CDCl3): δ 25.59 (d, JSiF = 287.6).
[Ir{K-P,Si-Si(F)(Me)CH2CH2CH2PPh2}(K-C,P-CH2CH2CH2-
PPh2)(NCMe)2]BF4 (12). The evolution of a NMR sample of 11
(15 mg, 0.02 mmol) in 0.5 mL of CDCl3 was monitored over a
period of 2 weeks. After this period, 11 was mostly transformed
1
into 12. Partial data for 12: H NMR (CDCl3): 7.16 (m, 20H,
CH), 2.91, 2.43 (both m, 1H, CH2), 2.19 (s, 3H, NCCH3), 2.15,
2.07 (both m, 1H, CH2), 1.92 (s, 3H, NCCH3), 1.87, 1.84, 1.82,
1.54, 1.46, 1.33, 0.85, 0.21 (all m, 1H, CH2), -0.51 (d, JHF = 8.1,
3H, CH3). 31P{1H} NMR (CDCl3): δ 9.41 (AB spin system),
δA = 27.9, δB = -9.4, JAB = 314.8). 13C{1H} NMR (CDCl3): δ
122.22, 122.09 (both s, NCCH3), 27.66 (d, JCP = 35.5, CH2),
27.69 (d, JCP = 38.6, CH2), 18.57 (s, CH2), 17.52 (m, CH2), 3.78
(s, NCCH3), 3.45 (d, JCF = 15.1, CH3), 3.02 (s, NCCH3), 0.08
(m, CH2), -2.00 (br, IrCH2). The crystals used in the X-ray
diffraction experiment were obtained upon cooling this NMR
sample.
[Ir(Et)H(biPSiOH)(NCMe)](CF3SO3) (9). Ethylene was bub-
bled during 1 min through a 0.5 mL CDCl3 solution of 7 (30 mg,
0.03 mmol) in a NMR tube. The resulting solution was periodically
monitored by NMR. The initial reaction product 8 was slowly
transformed into 9, which became the major reaction product after
1
about 2 weeks at room temperature. H NMR (CDCl3): δ 7.97
(m, 4H, CH), 7.39 (m, 16H, CH), 6.21 (s, 1H, OH), 2.99, 2.32, 1.85
(all m, 2H each, CH2), 1.65 (s, 3H, NCCH3), 1.55 (m, 2H, CH2),
1.46 (m, 2H, IrCH2CH3), 1.21, 0.51 (both m, 2H each, CH2), 0.42
(s,3H,CH3),-0.11(t,JHH =7.2,3H,IrCH2CH3),-19.18 (t, JHP
=
14.8, 1H, IrH). 31P{1H} NMR (CDCl3): δ 14.40 (s). 13C{1H}
NMR (CDCl3):δ134.99 (t, JCP = 5.5, CH), 134.35 (t, JCP = 21.4, C),
131.44 (t, JCP = 4.8, CH), 129.07, 128.61 (both s, CH), 128.40
Kinetic Studies. The exchange between free acetonitrile and
the acetonitrile ligands of isomers 3 was studied by 1H NMR in
solutions of 3 (approximately 0.06 M) containing acetonitrile
excess. Experiments were carried out in CD2Cl2 solution with
the exception of those at 312 K and above, which used CDCl3 as
solvent. The NMR sample temperature was calibrated using the
temperature dependence of the chemical shifts of methanol and
(t, JCP = 5.5, CH), 127.79 (t, JCP = 4.1, CH), 122.33 (q, JCF
=
320.1, CF3), 116.45 (s, NCCH3), 27.55 (t, JCP = 16.5, PCH2), 18.89
(s, IrCH2CH3), 17.13, 14.98 (both s, CH2), 2.81 (s, NCCH3), -2.75
(s, CH3), -27.86 (t, JCP = 4.8, IrCH2).

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10657
Table 3. Rate Constants (kobs, s-1) for the Exchange between the Acetonitrile
Ligands of Isomers 3 and Free Acetonitrile
with the SADABS program.32 The structures were solved by the
Patterson method and refined by full-matrix least-squares on F2
using the Bruker SHELXTL program package,33 including
isotropic and subsequently anisotropic displacement param-
eters. Weighted R factors (Rw) and goodness of fit (S) are
based on F2, and conventional R factors are based on F. The
OH hydrogen and the hydride ligands of 7 and 8 were located in
the difference Fourier maps but did not refined properly.
Restrained geometries (7 and 8) and restrained thermal parameters
(8) were used in the last cycles of refinement. The rest of the
hydrogen atoms were calculated using a restricted riding model on
their respective carbon atoms with the thermal parameter related
to the bonded atom. Disordered CH2Cl2 and diethyl ether mole-
cules were observed for 8. These molecules were refined with
restraints in both the geometry and the thermal parameters. All
the highest electronic residuals were observed in close proximity of
the Ir centers and make no chemical sense.
3-syn
3-anti
T (K) [NCMe]/[Ir] trans to Sib trans to H trans to Sib trans to H
208
213
217
221
221
223
227
232
236
236
240
245
252
293
298
302
306
306
306
307
308
312
316
320
324
1
1
1
1
10
1
1
1
1
10
1
1
1
1
1
1
1
3
0.71
2.0
3.0
5.8
5.6
0.62
1.5
3.5
5.6
5.7
14a
40a
101a
Data for 7. C34H41F3IrNO4P2SSi, M = 898.97; colorless
0.61
1.1
2.0
2.9
2.4
2.6
3.7
4.8
9.1
13a
22a
35a
irregular block, 0.10 ꢀ 0.06 ꢀ 0.06 mm3; monoclinic, P21/n;
˚
a =10.8199(5), b = 10.1125(5), c = 32.9470(16) A; β =
3
-3
˚
90.8420(10); Z = 4; V = 3604.5(3) A ; Dc = 1.657 g cm
;
μ=3.938 mm-1, minimum and maximum transmission factors
0.719 and 0.805; 2θmax=58.16°; 44435 reflections collected, 9043
unique [R(int)=0.0583]; number of data/restraints/parameters
9043/3/435; final GoF 0.794, R1 = 0.0304 [6808 reflections
I > 2σ(I)], wR2=0.0448 for all data; largest difference peak
10
1
1
1
1
-3
˚
1.676 e A
.
Data for 8. C34H42F3IrO4P2SSi 0.5OEt2 0.4CH2Cl2, M =
1
1
2.5
3
3
955.48; colorless irregular block, 0.07 ꢀ 0.04 ꢀ 0.01 mm3;
a From line width. b The 1H NMR signals corresponding to aceto-
nitriles trans to Si are not observable in the room temperature spectrum:
δ (208 K): 3-syn, 0.99 (s); 3-anti, 1.26 (s).
˚
triclinic, P1; a=8.8088(12), b=12.3483(17), c=18.596(3) A;
3
˚
R=81.914(2), β=80.057(2), γ=87.371(2); Z=2; V=1972.1(5) A ;
Dc=1.609 g cm-3; μ=3.656 mm-1, minimum and maximum
transmission factors 0.705 and 0.898; 2θmax = 57.50°; 17650
reflections collected, 9277 unique [R(int)=0.0512]; number of
data/restraints/parameters 9277/76/518; final GoF 0.962, R1=
0.0538 [7452 reflections I > 2σ(I)], wR2=0.1050 for all data;
ethylenglycol. Pseudo-first order rate constants (kobs) for each
individual exchange process were obtained by spin saturation
30
ꢀ
transfer following the Forsen-Hoffman method. The pre-
saturation pulse was applied on the 1H NMR signal of free
acetonitrile, and its effect was measured in the intensity of each
of the signals corresponding to coordinated acetonitrile ligands.
For some of the acetonitrile ligands (Table 3), the temperature
range of the kinetic determinations could be extended using rate
constants derived from the line-width of their 1H NMR signals.
After verifying that rate constants were independent upon
acetonitrile concentration (first-order), they were used to esti-
mate the activation parameters for the various acetonitrile
dissociations via Ln(kobs/T) versus 1/T regressions (Eyring
representations). Errors in ΔHq and ΔSq were estimated through
conventional error propagation formulas,31 assuming 1 K error
in the temperature and a 10% error in the rate constant.
-3
˚
largest difference peak 1.764 e A
Data for 12. C35H41BF5IrN2P2Si, M = 877.74; colorless
.
irregular block, 0.08 ꢀ 0.06 ꢀ 0.04 mm3; monoclinic, P21/n;
˚
a=11.1805(8), b=9.5246(7), c=33.037(2) A; β=95.9480(10);
Z=4; V=3499.1(4) A ; Dc=1.666 g cm-3; μ=3.997 mm-1
,
3
˚
minimum and maximum transmission factors 0.661 and 0.837;
2θmax=58.10°; 42818 reflections collected, 8723 unique [R(int)=
0.0919]; number of data/restraints/parameters 8723/6/428; final
GoF 0.883, R1 = 0.0447 [5685 reflections I > 2σ(I)], wR2 =
-3
˚
0.0740 for all data; largest difference peak 2.179 e A
.
Acknowledgment. This research was supported by the
Spanish MICINN (Project CTQ2009-08023 and Consolider
Ingenio 2010 INTECAT CSD2006-0003) and the Gobierno de
Crystallography. X-ray data were collected at 100.0(2) K on a
Bruker SMART APEX CCD with graphite-monochromated
˚
ꢀ
Aragon (Group E-79 and Project PI007/09).
Mo KR radiation (λ = 0.71073 A). Data were collected over the
complete sphere by a combination of four sets. Data were
corrected for absorption by using a multiscan method applied
Supporting Information Available: X-ray crystallographic file
for the complexes 7, 8, and 12 in CIF format. This material is
available free of charge via the Internet at http://pubs.acs.org.
(30) (a) Faller, J. W. In Determination of Organic Structures by Physical
Methods; Nachod, F. C., Zuckerman, J. J., Eds.; Academic Press: New York and
London, 1973. (b) Sanders, J. K. M.; Hunter, B. K. Modern NMR Spectroscopy,
A Guide for Chemists, 2nd ed.; Oxford University Press: Oxford, 1993.
(31) (a) Taylor, J. R. An Introduction to Error Analysis, 2nd ed.; University
Science Books: Mill Valley, CA, 1982. (b) Morse, P. M.; Spencer, M. O.; Wilson,
S. R.; Girolami, G. S. Organometallics 1994, 13, 1646–1655.
(32) Blessing, R. H. Acta Crystallogr. 1995, A51, 33–38. SADABS:
Area-detector absorption correction; Bruker- AXS: Madison, WI, 1996.
(33) SHELXTL, Package v. 6.10; Bruker-AXS: Madison, WI, 2000. Sheldrick,
€
€
G. M. SHELXS-86 and SHELXL-97; University of Gottingen: Gottingen, Germany,
1997.