Osmium NHC complexes from alcohol-functionalized imidazoles and imidazolium salts

Article abstract of DOI:10.1021/om101173e

The hexahydride complex OsH₆(PⁱPr₃) ₂ (1) reacts with 1-mesitylimidazole, 1-methylimidazole, 1-(2-hydroxy-2-phenylethyl)imidazole, and 1-(2-hydroxypropyl)imidazole to give the N-bound imidazole compounds OsH₄(RIm)(PⁱPr ₃)₂ (R = Mes (2), Me (3), CH₂CH(OH)Ph (4), CH₂CH(OH)CH₃ (5)) and H₂. In toluene under reflux the alcohol derivatives 4 and 5 evolve into the C-bound imidazole complexes OsH₃{CNHCHCHNCH=C(R)O}(PⁱPr₃) ₂ (R = Ph (6), CH₃ (7)), bearing an NH wingtip. These NHC-enolate species result from the N-bound to C-bound transformation of the heterocycle and the deprotonation-dehydrogenation of the alcohol substituent. The addition of HBF₄ to 6 and 7 affords the NHC-keto derivatives [OsH₃{CNHCHCHNCH₂C(R)=O}(PⁱPr₃) ₂]BF₄ (R = Ph (8), CH₃ (9)). Treatment of 1 with 3-benzyl-1-(2-hydroxy-2-phenylethyl)imidazolium tetrafluoroborate and 3-benzyl-1-(2-hydroxypropyl)imidazolium tetraphenylborate leads to the NHC-keto complexes [OsH₃{CN(CH₂Ph)CHCHNCH₂C(R)=O}(P ⁱPr₃)₂]A (A = BF₄, R = Ph (10); A = BPh₄, CH₃ (11)), as a consequence of the direct metalation of the heterocycle and the dehydrogenation of the alcohol substituent. The deprotonation of 10 and 11 with K^tBuO gives the NHC-enolate derivatives OsH₃{CN(CH₂Ph)CHCHNCH=C(R)O}(P ⁱPr₃)₂ (R = Ph (12), CH₃ (13)). The X-ray diffraction structures of 2, 6, and 10 are also reported.

Full text of DOI:10.1021/om101173e

ARTICLE
pubs.acs.org/Organometallics
Osmium NHC Complexes from Alcohol-Functionalized Imidazoles and
Imidazolium Salts†
Beatriz Eguillor,‡ Miguel A. Esteruelas,*,‡ Jorge García-Raboso,‡ Montserrat Olivꢀan,*,‡ Enrique O~nate,‡
Isidro M. Pastor,§ Itziar Pe~nafiel,§ and Miguel Yus*,§
‡Departamento de Química Inorgꢀanica-Instituto de Ciencia de Materiales de Aragꢀon, Universidad de Zaragoza-CSIC,
50009 Zaragoza, Spain
§Departamento de Química Orgꢀanica, Facultad de Ciencias and Instituto de Síntesis Orgꢀanica (ISO), Universidad de Alicante,
Apdo. 99, 03080 Alicante, Spain
S Supporting Information
b
ABSTRACT: The hexahydride complex OsH6(PiPr3)2 (1) reacts with 1-mesi-
tylimidazole, 1-methylimidazole, 1-(2-hydroxy-2-phenylethyl)imidazole, and
1-(2-hydroxypropyl)imidazole to give the N-bound imidazole compounds OsH4-
(RIm)(PiPr3)2 (R = Mes (2), Me (3), CH2CH(OH)Ph (4), CH2CH(OH)CH3
(5)) and H2. In toluene under reflux the alcohol derivatives 4 and 5 evolve into
the C-bound imidazole complexes OsH3{CNHCHCHNCHdC(R)O}(PiPr3)2 (R = Ph (6), CH3 (7)), bearing an NH wingtip.
jj
j
These NHC-enolate species result from the N-bound to C-bound transformation of the heterocycle and the deprotonation-
dehydrogenation of the alcohol substituent. The addition of HBF4 to 6 and 7 affords the NHC-keto derivatives
[OsH3{CNHCHCHNCH2C(R)dO}(PiPr3)2]BF4 (R = Ph (8), CH3 (9)). Treatment of 1 with 3-benzyl-1-(2-hydroxy-2-
jj
j
phenylethyl)imidazolium tetrafluoroborate and 3-benzyl-1-(2-hydroxypropyl)imidazolium tetraphenylborate leads to the NHC-
keto complexes [OsH3{CN(CH2Ph)CHCHNCH2C(R)dO}(PiPr3)2]A (A = BF4, R = Ph (10); A = BPh4, CH3 (11)), as a con-
jj
j
sequence of the direct metalation of the heterocycle and the dehydrogenation of the alcohol substituent. The deprotonation of
10 and 11 with KtBuO gives the NHC-enolate derivatives OsH3{CN(CH2Ph)CHCHNCHdC(R)O}(PiPr3)2 (R = Ph (12), CH3
jj
j
(13)). The X-ray diffraction structures of 2, 6, and 10 are also reported.
’ INTRODUCTION
afford labile Brønsted acid ligands as a result of the deprotonation
of the imidazolium salt. Unfortunately, the basic precursors are
limited to [M(μ-OMe)(diolefin)]2 (M = Rh, Ir)6 and M(OAc)2
(M = Ni,7 Pd,8 Pt9). Recent reports have shown that these
compounds can undergo transformations via a range of NHC
reactions,10 including migratory insertion,11 N-substituent
cleavage,12 ring expansion involving heterocyclic N-C bond
cleavage,13 and C-H14 and C-C15 bond activation of the
N-alkyl or N-aryl substituents.
N-heterocyclic carbenes (NHCs) are cyclic “Fischer-type”
ligands bearing at least one R-amino substituent.1 During the
past few years, their chemistry has experienced explosive devel-
opment, due to the design of diverse homogeneous catalytic
systems comprising such carbene ligands2 and use of NHC
complexes as antimicrobial and cytotoxic agents,3 as photoactive
sites in luminescent materials for self-assembly into liquid
crystalline materials and metallosupramolecular structures, and
as synthons for molecular switches and conducting polymeric
materials.4
The vast majority of reported NHC ligands are substituted at
nitrogen(s) by alkyl or aryl groups. Deprotonation of imidazo-
lium salts and transmetalation from silver are the most used
synthetic pathways for the preparation of complexes containing
these ligands.5 However, the cleanest synthetic strategy is
undoubtedly direct metalation. This method requires the pre-
sence at the starting complex of strong Brønsted bases, which
Imidazolium salts with carbonyl,16 pyridyl,16a,17 pyrazolyl,18
amine,19 and phosphine20 substituents are also known. They can
be deprotonated and are thus suitable for the preparation of
metal complexes. Alcohol-functionalized imidazolium salts are
readily accessible by the nucleophilic opening of epoxides.21 The
alcohol function appears to be more acidic than the heterocycle.
A single deprotonation leads to a zwitterionic alcoholate
Received: December 15, 2010
Published: February 24, 2011
r
2011 American Chemical Society
1658
dx.doi.org/10.1021/om101173e Organometallics 2011, 30, 1658–1667
|

Organometallics
ARTICLE
imidazolium derivative. However, the reaction with 2 equiv of
base yields the alkali-metal carbene adducts, which have been
shown to be carbene transfer agents for the preparation of
transition-metal complexes with these functionalized NHC
ligands.22 Direct metalation has been not explored.
Scheme 1
There are also some C-bound imidazole derivatives bearing
an NH wingtip.23 The limited number of examples of this
type is chiefly because tautomerization to the N-bound imida-
zole,12b,23e,24 a 1,3-ligand to metal hydrogen shift,25 or deproto-
nation to form an anionic ligand23g,h may occur. Stable C-bound
imidazole complexes have been prepared by tautomerization
of N-bound imidazole precursors,23a,c,d,f,h-j,l coupling of iso-
cyanides with propargylamines,23b,g,k and deprotection of
N-acyl-substituted NHC complexes.23e,m The imidazole tauto-
mer is more stable than the carbene form for free ligands.26
However, theoretical calculations suggest that, once coordinated
to a metal, either the N- or C-bound form can be thermodyna-
mically favored, depending on the environment of the metal.27
Some cases of NH-bearing carbenes derived from pyridines have
been also reported.28
The saturated d2 hexahydride complex OsH6(PiPr3)2 activates
C-H bonds of different organic substrates29 and, by protonation
with weak Brønsted acids, releases molecular hydrogen, affording
d4 species, which contain the corresponding conjugated Brønsted
base as a ligand.30 In agreement with this, it also reacts with
N-alkyl and N-aryl imidazolium salts to give osmium derivatives
with normal and abnormal NHC ligands.17f,31 In the search for
direct metalation for alcohol-functionalized imidazole and imi-
dazolium salts, we have now studied the reactivity of the
hexahydride complex toward these types of NHC precursors.
This paper reports (i) the formation of d4 osmium tetrahy-
dride compounds containing N-bound imidazole ligands, (ii)
their transformation to C-bound derivatives bearing an NH
wingtip, and (iii) O-functionalized, N-disubstituted osmium
NHC complexes formed by direct metalation of alcohol-functio-
nalized imidazolium salts.
’ RESULTS AND DISCUSSION
Figure 1. Molecular diagram of complex 2. Selected bond lengths (Å)
and angles (deg): Os-P(1) = 2.3223(13), Os-P(2) = 2.3185(13), Os-
N(1) = 2.159(4), H(1A) H(1C) = 1.61(4), H(1C) H(1B) =
1. N-Bound Imidazole Complexes. Treatment between 5
and 17 h of tetrahydrofuran solutions of the hexahydride OsH6-
(PiPr3)2 (1) with 1.2 equiv of 1-mesitylimidazole, 1-methylimi-
dazole, 1-(2-hydroxy-2-phenylethyl)imidazole, and 1-(2-hydro-
xypropyl)imidazole under reflux leads to the tetrahydride
derivatives OsH4(Rim)(PiPr3)2 (R = Mes (2), Me (3), CH2CH-
(OH)Ph (4), CH2CH(OH)CH3 (5)), containing a N-bound
imidazole ligand. These compounds were isolated as white solids
in 26-89% yields, according to Scheme 1.
Complex 2 has been characterized by X-ray diffraction anal-
ysis. Its structure (Figure 1) proves the N-bound coordination of
the heterocycle in these species. The geometry around the
osmium atom can be rationalized as a distorted pentagonal
bipyramid with axial phosphines (P(1)-Os-P(2) = 174.55(5)°).
The metal coordination sphere is completed by the hydride
ligands (H-H > 1.61(4) Å), and the imidazole group, which lies
between H(1A) and H(1D). The Os-N(1) bond length of
2.159(4) Å compares well with the osmium-pyridine separation
in the related compound OsH4(py)(PiPr3)2 (2.162(6) Å).29i
The 31P{1H} and 1H NMR spectra of 2-5 in toluene-d8 are
consistent with the structure shown in Figure 1. In agreement
with equivalent phosphines, the 31P{1H} spectra contain a
singlet at about 44 ppm, whereas, according to the presence of
3 3 3
3 3 3
1.81(5), H(1B) H(1D) = 1.68(5); P(1)-Os-P(2) = 174.55(5),
3 3 3
P(1)-Os-N(1) = 90.99(10), P(2)-Os-N(1) = 94.11(10).
four inequivalent hydride ligands, the 1H NMR spectra at 193 K
show four hydride resonances between -4 and -16 ppm.
2. C-Bound Imidazole Complexes: Influence of the Alco-
hol Function on the Coordination Mode of the Heterocycle.
The substituent of the imidazole group has a marked influence on
the behavior of the heterocycle of these systems. In contrast to 2
and 3, which remain unaltered after 17 h in toluene under reflux,
the alcohol derivatives 4 and 5 evolve into the C-bound imidazole
complexes OsH3{CNHCHCHNCHdC(R)O}(PiPr3)2 (R =
jj
j
Ph (6), CH3 (7)) in quantitative yield, according to eq 1. In
addition to the N-bound to C-bound transformation of the
heterocycle, the formation of these compounds implies the
release of two hydrogen molecules. One of them results from
the protonation of the OsH4 units of 4 and 5 with the alcohol
function of the ligands, whereas the other is generated by
dehydrogenation of the aliphatic chain. Complexes 6 and 7 are
1659
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
Figure 2. (a) Molecular diagram of complex 6. Selected bond lengths (Å) and angles (deg): Os-P(1) = 2.3223(16), Os-P(2) = 2.3474(17), Os-O =
2.172(4), Os-C(1) = 2.102(6), N(2)-C(4) = 1.422(7), C(4)-C(5) = 1.334(8), C(5)-O = 1.306(6), H(01)-H(02) = 1.54(1), H(02)-H(03) =
1.57(5), H(01)-H(1) = 2.53; P(1)-Os-P(2) = 166.31(6), O-Os-C(1) = 85.21(19). (b) Optimized structure (B3PW91) of complex 6. Selected bond
lengths (Å) and angles (deg): H(01) H(02) = 1.573, H(02) H(03) = 1.689, H(01) H(1) = 2.241; H(01)-Os-H(02) = 58.6, H(02)-Os-
3 3 3
3 3 3
3 3 3
H(03) = 62.4.
isolated as green solids in moderate yields (30-60%) due to their
high solubility in the usual precipitating agents.
applied to the synthesis of aromatic heterometallacyclic com-
pounds. In this case, a hydrogen acceptor is not necessary, even
under mild conditions.35 The aliphatic dehydrogenation in 4 and
5 is consistent with the latter.
The 1H, 13C{1H}, and 31P{1H} NMR spectra of 6 and 7 agree
well with the structures shown in Figure 2. In the 1H NMR spectra
the most noticeable feature is the presence of the NH resonances,
which appear at 7.68 (6) and 7.64 ppm (7) . The CH protons of the
six-membered heterometallaring display singlets at 6.33 (6) and 5.47
ppm (7). In the high-field region, the spectrum of 6 at 139 K in
CDCl2F contains two broad resonances at -5.0 and -14.5 ppm,
whereas that of 7 shows three resonances at -5.51, -13.41, and -
16.87 ppm, in agreement with the presence of three inequivalent
hydride ligands in these compounds. In the 13C{1H} NMR spectra
the OsC resonances are observed at 169.2 (6) and 167.4 ppm (7),
as triplets with C-P coupling constants of about 8 Hz, whereas
the OC and CH carbon atoms of the six-membered ring display
singlets at 151.5 and 97.2 ppm (6) and 152.3 and 95.5 ppm (7).
As expected for equivalent phosphine ligands, the 31P{1H} NMR
spectra contain singlets at 31.5 (6) and 31.4 ppm (7).
Figure 2a shows a view of the structure of 6. The coordination
geometry around the osmium atom can be rationalized as a distorted
pentagonal bipyramid with the phosphorus atoms of the phosphine
ligands occupying axial positions (P(1)-Os-P(2) = 166.31(6)°).
The osmium sphere is completed by the hydride ligands and the
chelate group, which has a bite angle C(1)-Os-O of 85.21(19)°.
The B3PW91 optimized structure (Figure 2b) confirms the trihy-
dride character of the OsH3 unit. The H(01)-H(02) and H(02)-
H(03) separations are 1.573 and 1.689 Å, whereas the H(01)-Os-
H(02) and H(02)-Os-H(03) angles are 58.6 and 62.4°. Further-
more, the calculations reveal that the distance between the NH
hydrogen H(1) and the hydride H(01) is short (2.241 Å) and lies
within the range reported for the H-H separations in rings of
Complexes 6 and 7 are Brønsted bases. Thus, the addition at
room temperature of 1.0 equiv of HBF4 to diethyl ether solutions
of these compounds produces the precipitation of the C-bound
the type LH- - -HM with an electrostatic hydrogen-hydrogen
interaction.28d,32 The osmabicycle is planar (maximum deviation
0.0376(33) Å for O). The Os-C(1) bond length of 2.102(6) Å
agrees well with those previously reported for Os-NHC com-
pounds with normal coordination of the NHC unit.15c,17f,31,33 The
Os-O bond length of 2.172(4) Å compares well with those found
in lower π-electron osmacyclic oxygen-containing compounds,28i
whereas the C(4)-C(5) and C(5)-O distances of 1.334(8) and
1.306(6) Å, respectively, lie between those expected for single and
double bonds. This indicates electron delocalization between C(4)
and O, which appears to be the driving force for the dehydrogenation
of the aliphatic chain of the substituent of the heterocycles.
imidazole-keto derivatives [OsH3{CNHCHCHNCH2C(R)dO}-
jj
j
(PiPr3)2]BF4 (R = Ph (8), CH3 (9)) as a result of the addition of
the proton of the acid to the β-carbon atom of the enolate units of 6
and 7 (eq 2). The reaction is reversible; treatment of 8 and 9 with
KtBuO in tetrahydrofuran regenerates 6 and 7.
Aliphatic dehydrogenation is a strongly endothermic process.
The equilibrium can be shifted to the right, however, by adding a
hydrogen acceptor. The presence of a transition-metal catalyst
facilitates the hydrogen transfer.34 Recently, we have shown that
the aromatization by dehydrogenation is a method which can be
Complexes 8 and 9 are isolated as brown solids in 56 and
96% yields, respectively. The 1H, 13C{1H}, and 31P{1H} NMR
1660
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
Figure 3. (a) Molecular diagram of the cation of 10. Selected bond lengths (Å) and angles (deg): Os-P(1) = 2.3438(11), Os-P(2) = 2.3631(11), Os-
O(1) = 2.157(2), Os-C(1) = 2.107(4), H(01) H(02) = 1.58(3), H(02) H(03) = 1.67(3); P(1)-Os-P(2) = 164.85(3), O-Os-C(1) =
3 3 3
3 3 3
82.65(11). (b) Optimized structure (B3PW91) of the cation of complex 10. Selected bond lengths (Å) and angles (deg): H(01) H(02) = 1.605,
3 3 3
H(02) H(03) = 1.611; H(01)-Os-H(02) = 60.2, H(02)-Os-H(03) = 59.5.
3 3 3
spectra of these compounds strongly support the structure
proposed in eq 2. In agreement with the presence of three
inequivalent hydride ligands, the H NMR spectra at 189 K
and H(03) hydrogen atoms. The B3PW91 optimized structure
(Figure 3b) supports the trihydride character of the OsH3 unit.
The H(01)-H(02) and H(02)-H(03) separations are 1.605 and
1.611 Å, respectively, whereas the H(01)-Os-H(02) and H(02)-
Os-H(03) angles are 60.2 and 59.5°, respectively. The chelate
group has an O-Os-C(1) bite angle of 82.65(11)° and forms a six-
membered ring with the metal center with a boat conformation. The
Os-C(1) and Os-O(1) bond lengths of 2.107(4) and 2.157(2) Å,
respectively, are statistically identical with those of 6.
1
in CD2Cl2 contain three high-field resonances between -7
and -17 ppm. The NH resonances are observed at 9.50 (8)
and 9.61 ppm (9), whereas the signals corresponding to the CH2
groups of the six-membered rings appear at 6.15 (8) and 5.62
ppm (9). The 13C{1H} spectra reveal the presence of the keto
function in the compounds, showing singlets at 192.0 (8) and
206.0 ppm (9). The OsC NHC resonances are observed at 176.1
(8) and 176.3 ppm (9), as triplets with C-P coupling constants
of about 7 Hz. According to the presence of equivalent phos-
phines, the 31P{1H} NMR spectra show singlets at about 29 ppm.
3. Direct Metalation of Alcohol-Functionalized Imidazo-
lium Salts. Treatment of tetrahydrofuran solutions of 1 with 1.2
equiv of 3-benzyl-1-(2-hydroxy-2-phenylethyl)imidazolium tetrafluo-
roborate and 3-benzyl-1-(2-hydroxypropyl)imidazolium tetraphenyl-
borate for 29 h under reflux leads to the NHC-keto derivatives
The 1H and 13C{1H} NMR spectra of 10 and 11 are consistent
with the structures shown in Figure 3. As expected for three
1
inequivalent hydride ligands, the H NMR spectra in CDCl2F at
181 K contain three high-field signals between -6 and -18 ppm. In
the 13C{1H} NMR spectra, the OsC NHC resonances are observed
at 183.5 (10) and 181.9 ppm (11) as triplets with C-P coupling
constants of about 6 Hz. In spite of the presence of inequivalent
phosphine ligands in these compounds, the 31P{1H} NMR spectra
show singlets at about 30 ppm, even at 143 K in CDCl2F.
Complexes 10 and 11 are as easily deprotonated as 8 and 9.
Treatment of tetrahydrofuran solutions of 10 and 11 with 2.0
equiv of KtBuO for 40 min at room temperature produces
the extraction of one of the hydrogen atoms of the CH2 groups
of the six-membered rings, to afford the NHC-enolate
[OsH3{CN(CH2Ph)CHCHNCH2C(R)dO}(PiPr3)2]A(A=BF4,
jj
j
R = Ph (10); A = BPh4, CH3 (11)) as a result of the direct meta-
lation of the imidazolium moieties and the dehydrogenation of the
alcohol functions. Complexes 10 and 11 are isolated as garnet and
yellow solids in 61% and 90% yields, respectively, according to eq 3.
derivatives OsH3{CN(CH2Ph)CHCHNCHdC(R)O}(PiPr3)2
jj
j
(R = Ph (12), R = CH3 (13)). The reaction is reversible; the
addition of 1.0 equiv of HBF4 to the diethyl ether solutions of 12 and
13 produces the precipitation of 10 and 11 as their BF4 salts (eq 4).
Figure 3a shows a view of the cation of 10. The structure proves
the metalation of the imidazolylidene group and the dehydrogena-
tion of the alcohol function. The geometry around the osmium atom
can be rationalized as a distorted pentagonal bipyramid with the
phosphine ligands occupying axial positions (P(1)-Os-P(2) =
164.85(3)°). The metal coordination sphere is completed by the
O and C(1) atoms of the chelate group and the H(01), H(02),
Complexes 12 and 13 are isolated as yellow solids in moderate
yields (40-50%). The 1H, 13C{1H}, and 31P{1H} NMR spectra
1661
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
of these compounds agree well with those of 6 and 7. At
low temperature, 138 K for 12 and 172 K for 13, the 1H NMR
spectra in CDCl2F shows three hydride resonances between -5
and -16 ppm. In this context we should mention the presence of
an AB spin system, in the 1H{31P} NMR spectrum of 13 at 172 K,
centered at -15 ppm and defined by JA-B = 288 Hz and Δν = 684,
which can be explained in terms of quantum exchange coupling36
between two of the hydride ligands. In the 13C{1H} NMR
spectra the OC resonances appear at 151.4 (12) and 152.4
ppm (13), shifted by 45.3 and 54.3 ppm, respectively, toward
higher field with regard to those of 10 (196.7 ppm) and 11 (206.7
ppm). The OsC NHC resonances are observed at 175.1 (12) and
173.8 ppm (13), as triplets with a C-P coupling constant of 7.5
Hz. The 31P{1H} NMR spectra between 290 and 193 K show
singlets at about 32 ppm.
imidazole,21 OsH6(PiPr3)2 (1),38 and CDCl2F39 were prepared by
published methods.
Preparation of 1-(2-Hydroxypropyl)imidazole. This mole-
cule was synthesized analogously as described in the literature21 starting
from imidazole and propylene oxide. It was isolated as a yellow oil in 85%
yield. HRMS: m/z calcd for C6H10N2O 126.0788, found 127.0869. IR
(cm-1): ν(O-H) 3112 (m). 1H NMR (400 MHz, CDCl3, 293 K): δ
7.30 (s, 1H, NCHN), 6.90 (s, 1H, CH im), 6.82 (s, 1H, CH im), 5.20 (s,
1H, OH), 3.97 (m, 1H, CHOH), 3.86 (dd, JH-H = 13.9, JH-H = 3.5, 1H,
CH2CHOH), 3.75 (dd, JH-H = 13.9, JH-H = 3.5, 1H, CH2CHOH), 1.14
(d, JH-H = 6.3, 3H, CH3). 13C{1H} NMR (100.62 MHz, CDCl3, 293
K): δ 138.0, 128.8, 120.4 (all s, CH im), 66.9 (s, CH(OH)), 55.2 (s,
CH2CH(OH)), 21.1 (s, CH3).
Preparation of 3-Benzyl-1-(2-hydroxy-2-phenylethyl)
imidazolium Chloride. Benzyl chloride (633 μL, 5.5 mmol) was
added at room temperature to a solution of 1-(2-hydroxy-2-pheny-
lethyl)imidazole (941 mg, 5.0 mmol) in acetonitrile (15 mL) placed in a
round-bottom flask, and the resulting mixture was stirred at 80 °C for
16 h. The resulting solution was evaporated to dryness, and acetone was
added to the residue to afford a white solid, which was washed with
further portions of acetone and dried in vacuo. Yield: 944 mg (60%).
Anal. Calcd for C18H19ClN2O: C, 68.76; H, 6.10; N, 8.91. Found: C,
69.11; H, 6.48; N, 9.05. HRMS: m/z calcd for C18H19N2O 279.1492,
found 279.1486. IR (cm-1): ν(O-H) 3213 (m). 1H NMR (400 MHz,
CDCl3, 293 K): δ 10.00 (s, 1H, NCHN), 7.45-7.25 (m, 10H, Ph), 7.22
(s, 1H, CH im), 6.99 (s, 1H, CH im), 6.34 (s, 1H, OH), 5.33 (s, 2H,
’ CONCLUDING REMARKS
This study has revealed that the hexahydride complex OsH6-
(PiPr3)2 promotes the N-bound to C-bound transformation and
the alcohol deprotonation-dehydrogenation of alcohol-functio-
nalized imidazoles and the imidazolium metalation and alcohol
dehydrogenation of alcohol-functionalized imidazolium salts. In
the first case NHC-enolate derivatives bearing an NH- wingtip
are obtained, whereas in the second case NHC-keto compounds
are formed. The conversion to the respective NHC-keto and
NHC-enolate is easily achieved by protonation and deprotona-
tion reactions.
The deprotonation-dehydrogenation process of the alcohol
substituent is determinant for the N-bound to C-bound trans-
formation of the imidazole moiety of these ligands. In contrast to
1-(2-hydroxy-2-phenylethyl)imidazole and 1-(2-hydroxypropyl)-
imidazole, 1-mesitylimidazole and 1-methylimidazole do not
undergo tautomerization. As in other related tautomerization
CH2Ph), 5.26 (dd, JH-H =7.6,JH-H =3.2, 1H, CH(OH)), 4.73(dd,JH-H
=
14.0, JH-H = 3.2, 1H, CH2CH(OH)), 4.39 (dd, J = 14.0, JH-H = 7.6, 1H,
CH2CH(OH)). 13C{1H} NMR (100.62 MHz, CDCl3, 293 K): δ 140.0
(s, Cipso Ph), 137.4 (s, NCHN), 132.7 (s, Cipso Ph), 129.4, 128.7, 128.5,
127.8, 126.0 (all s, CH Ph), 123.5, 120.6 (both s, CH im), 70.9 (s,
CH(OH)), 56.9 (s, CH2CH(OH)), 53.3 (s, CH2Ph).
Preparation of 3-Benzyl-1-(2-hydroxypropyl)imidazolium
Chloride. Benzyl chloride (633 μL, 5.5 mmol) was added at room
temperature to a solution of 1-(2-hydroxypropyl)imidazole (631 mg, 5.0
mmol) in acetonitrile (15 mL) placed in a round-bottom flask, and the
resulting mixture was stirred at 80 °C for 16 h. The resulting solution was
evaporated to dryness, and diethyl ether was added to the residue to
afford a yellow oil, which was washed with further portions of diethyl
ether and dried in vacuo. Yield: 1.00 g (72%). HRMS: m/z calcd for
C13H17N2O 217.1335, found 217.1322. IR (cm-1): ν(O-H) 3247
(m). 1H NMR (400 MHz, CDCl3, 293 K): δ 10.01 (s, 1H, NCHN), 7.60
processes,28a,d,e,i,j,q an intramolecular LM- - -HM hydrogen bond
between a hydride ligand and the NH hydrogen atom of the
C-bound heterocycle seems to contribute to the stabilization of
the formed species.
In conclusion, polyhydride complexes promote the N-bound
to C-bound transformation of alcohol-functionalized imidazole
and the metalation of alcohol-functionalized imidazolium
salts. The alcohol function is relevant for both processes. In addi-
tion to stabilizing by chelation the resulting species, it undergoes
dehydrogenation.
(s, 1H, CH im), 7.40 (m, 5H, Ph), 7.26 (s, 1H, CH im), 5.63 (d, JH-H
=
8, -OH), 5.48 (s, 2H, CH2Ph), 4.42 (m, 1H, CH2CH(OH)), 4.25 (m,
1H, CH2CH(OH)), 4.16 (m, 1H, CH(OH)), 1.23 (d, JH-H = 4.0, 3H,
CH3). 13C{1H} NMR (100.62 MHz, CDCl3, 293 K): δ 137.0 (s,
NCHN), 133.7 (s, Cipso Ph), 129.5, 129.9, 130.0 (all s, CH Ph), 124.3,
121.7 (both s, CH im), 66.4 (s, CH(OH)), 57.4 (s, CH2CH(OH)), 53.9
(s, CH2Ph), 20.9 (s, CH3).
’ EXPERIMENTAL SECTION
Anion Exchange of 3-Benzyl-1-(2-hydroxy-2-phenylethyl)
imidazolium Chloride to Give 3-benzyl-1-(2-hydroxy-2-phe-
nylethyl)imidazolium Tetrafluoroborate. A 1:1 mixture of the
imidazolium chloride salt and AgBF4 was stirred in acetone in the dark
for 12 h. The reaction mixture was filtered through Celite and the solvent
of the filtrate removed in vacuo. The salt that formed was used without
further purification.
Preparation of 3-Benzyl-1-(2-hydroxypropyl)imidazolium
Tetraphenylborate. 3-Benzyl-1-(2-hydroxypropyl)imidazolium chlor-
ide (77.3 mg, 0.31 mmol) and NaBPh4 (105 mg, 0.31 mmol) were
dissolved in acetone (6 mL) and MeOH (2 mL), and this mixture was
stirred for 2 h. The resulting solution was taken to dryness. Dichloro-
methane (10 mL) was added, giving a precipitate of NaCl. After filtering,
the resulting solution was evaporated to dryness. The addition of diethyl
ether to the residue afforded a white solid that was washed with diethyl
General Information. All reactions were carried out with rigor-
ous exclusion of air using Schlenk-tube techniques. Solvents (except
acetonitrile and acetone, which were dried and distilled under argon)
were obtained oxygen- and water-free from an MBraun solvent purifica-
tion apparatus. 1H, 31P{1H}, and 13C{1H} NMR spectra were recorded
on Bruker ARX 300 MHz, Bruker Avance 300 MHz, and Bruker Avance
400 MHz instruments. Chemical shifts (expressed in parts per million)
are referenced to residual solvent peaks (1H, 13C{1H}) or to external
85% H3PO4 (31P{1H}). Coupling constants J and N are given in hertz.
Infrared spectra were recorded on a Perkin-Elmer Spectrum 100
spectrometer as neat solids or oils. C, H, and N analyses were carried
out with a Perkin-Elmer 2400 CHNS/O analyzer. High-resolution
electrospray mass spectra were acquired using a MicroTOF-Q
hybrid quadrupole time-of-flight spectrometer (Bruker Daltonics,
Bremen, Germany). 1-Mesitylimidazole,37 1-(2-hydroxy-2-phenylethyl)
1662
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
ether (6 ꢁ 3 mL) and dried in vacuo. Yield: 94 mg (57%). Anal. Calcd
for C37H37BN2O: C, 82.83; H, 6.95; N, 5.22. Found: C, 83.15; H, 7.10;
N, 5.37. 1H NMR (300 MHz, CD2Cl2, 293 K): δ 7.42-6.83 (m, 26H,
CH im, Ph and BPh4), 6.62 (s, 1H, CH im), 5.95 (s, 1H, CH im), 4.62 (s,
2H, CH2Ph), 4.59 (s, 1H, OH), 3.61 (m, 1H, CH(OH)), 3.30 (m, 2H,
CH2CH(OH)), 1.08 (d, JH-H = 6.3, 3H, -CH3). 13C{1H} NMR
(75.47 MHz, CD2Cl2, 293K): δ 164.4 (q, JB-C = 36.9, Cipso BPh4),
136.1 (s, CH BPh4), 135.7 (s, NCHN), 132.3 (s, Cipso Ph), 129.9, 129.8,
128.6 (all s, CH Ph), 126.4 (q, JB-C = 2, CH BPh4), 123.5 (s, CH im),
122.4 (s, CH BPh4), 121.2 (s, CH im), 66.3 (s, -CH(OH)), 56.1
(s, -CH2CH(OH)), 53.6 (s, CH2Ph), 20.9 (s, -CH3).
(m, 2H, N-CH2), 1.84 (m, 6H, PCH(CH3)2), 1.35 (dvt, JH-H = 6.4,
1
N = 12, 36H, PCH(CH3)2), -9.63 (br, 4H, Os-H). H{31P} NMR
(300 MHz, toluene-d8, 183 K, high-field region): δ -4.8 (br, 1H, Os-
H), -4.9 (br, 1H, Os-H), -14.3 (br, 1H, Os-H), -14.4 (br, 1H, Os-
H). 31P{1H} NMR (161.9 MHz, C6D6, 298 K): δ 44.2 (s). 13C{1H}
APT NMR plus HSQC (100.62 MHz, C6D6, 298 K): δ 150.2 (s,
NCHN), 141.8 (s, Cipso Ph), 140.3 (s, CH im), 128.3, 127.0, 126.1 (all s,
CH Ph), 119.7 (s, CH im), 73.0 (s, CHOH), 53.9 (s, CH2), 27.4 (vt, N =
21.9, PCH(CH3)2), 20.7 (s, PCH(CH3)2).
Preparation of OsH4[CH3CH(OH)CH2Im](PiPr3)2 (5). A col-
orless solution of 1 (132 mg, 0.26 mmol) in THF (10 mL) was treated
with 1.2 equiv of 1-(2-hydroxypropyl)imidazole (38.7 mg, 0.31 mmol)
and heated under reflux for 5 h. The resulting solution was filtered
through Celite and was taken to dryness. Addition of methanol to the
residue at 223 K afforded a white solid that was washed with methanol
and dried in vacuo. 1H and 31P{1H} NMR spectra show that the reaction
is quantitative, but the obtained yield is very low due to the high
solubility of the complex in methanol. Yield: 43 mg (26%). Anal. Calcd
for C24H56N2OOsP2: C, 44.97; H, 8.08; N, 4.37. Found: C, 45.13;
H, 8.17; N, 4.55. IR (cm-1): ν(OsH) 2105 (w), ν(CdN) 1786 (s).
1H NMR (300 MHz, C6D6, 298 K): δ 7.76 (s, 1H, NCHN), 7.37 (s,
1H, CH im), 6.04 (s, 1H, CH im), 3.63 (br, 1H, -OH), 3.33 (m,
H, -CH(OH)CH3), 2.95 (m, 2H, -CH2-), 1.86 (m, 6H, PCH-
(CH3)2), 1.35 (dvt, JH-H = 6.4, N = 11.7, 36H, PCH(CH3)2), 0.64 (d,
JH-H = 6.2, 3H, CH3), -9.56 (br, 4H, Os-H). 1H{31P} NMR (C7D8,
400 MHz, 193 K, high-field region): δ -5.1 (br, 1H, Os-H), -5.3 (br,
1H, Os-H), -14.1 (br, 1H, Os-H), -14.5 (br, 1H, Os-H). 31P{1H}
NMR (121.49 MHz, C6D6, 298 K): δ 43.7 (s). 13C{1H} APT NMR plus
HSQC (75.47 MHz, C6D6, 298 K): δ 146.1 (s, NCHN), 140.7 (s, CH
im), 119.6 (s, CH im), 66.4 (s, CHOH), 53.5 (s, -CH2-), 27.54 (vt, N =
22, PCH(CH3)2), 20.6 (s, PCH(CH3)2), 20.1 (s, -CH3).
Preparation of OsH4(MesIm)(PiPr3)2 (2). A solution of 1 (150
mg, 0.291 mmol) in THF (20 mL) was treated with the stoichiometric
amount of 1-mesitylimidazole (54.1 mg, 0.291 mmol). The resulting
solution was stirred at 90 °C for 6 h. After it was cooled to room
temperature, the solution was filtered through Celite and the solvent
removed. Addition of methanol to the residue at 223 K afforded a white
solid that was washed with methanol and dried in vacuo. Yield: 182 mg
(89%). Anal. Calcd for C30H60N2OsP2: C, 51.40; H, 8.63; N, 4.00.
Found: C, 51.57; H, 8.33; N, 4.20. IR (cm-1): ν(Os-H) 2102 (w);
ν(CdN) 1785 (s). 1H NMR (300 MHz, C6D6, 293 K): δ 7.72 (s, 1H,
NCHN), 7.40 (s, 1H, CH im), 6.95 (s, 2H, CH mes), 6.49 (s, 1H, CH
im), 2.30 (s, 3H, p-CH3), 1.91 (s, 6H, o-CH3), 1.68 (m, 6H, PCH-
(CH3)2), 1.14 (dvt, JH-H = 6, N = 12, 36H, PCH(CH3)2), -10.11 (br,
1
4H, OsH). H{31P} NMR (300 MHz, toluene-d8, 183 K, high-field
region): δ -5.4 (br, 1H, Os-H), -5.6 (br, 1H, Os-H), -15.1 (br, 1H,
Os-H), -15.2 (br, 1H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6,
293 K): δ 44.6 (s). 13C{1H} NMR (75.42 MHz, C6D6, 293 K, plus apt):
δ 145.5 (s, NCHN), 141.3 (s, CH im), 139.5 (s, mes), 135.5 (s, mes),
132.8 (s, mes), 129.3 (s, CH mes), 120.5 (s, CH im), 27.1 (vt, N = 22.2,
PCH(CH3)2), 21.1 (s, p-CH3 mes), 20.3 (s, PCH(CH3)2), 17.2 (s,
o-CH3 mes).
Preparation of OsH4(MeIm)(PiPr3)2 (3). A solution of 1 (100
mg, 0.19 mmol) in THF (15 mL) was treated with 1.2 equiv of
1-methylimidazole (18.5 μL, 0.23 mmol). The resulting solution was
heated under reflux for 6 h. After it was cooled to room temperature, the
resulting solution was filtered through Celite and the solvent removed.
Pentane was added to afford a solution that was cooled overnight to
afford a white solid, which was washed with further portions of pentane
and dried in vacuo. Yield: 53 mg (46%). Anal. Calcd for C22H52N2OsP2:
C, 44.27; H, 8.78; N, 4.69. Found: C, 44.33; H, 8.53; N, 4.86. IR (cm-1):
ν(Os-H) 2123 (w), ν(CdN) 1769 (s). 1H NMR (300 MHz, toluene-
d8, 293 K): δ 7.43 (s, 1H, NCHN), 7.24 (s, 1H, OsNCH), 5.50 (s, 1H,
CHNCH3), 2.18 (s, 3H, CH3), 1.73 (m, 6H, PCH(CH3)2), 1.32 (dvt,
JH-H = 5.7, N = 12, 36H, PCH(CH3)2), -9.70 (br t, 4H, OsH).
1H{31P} NMR (300 MHz, toluene-d8, 203 K, high-field region): δ -4.7
(br, 1H, Os-H), -4.8 (br, 1H, Os-H), -14.3 (br, 1H, Os-H), -14.4
(br, 1H, Os-H). 31P{1H} NMR (121.5 MHz, toluene-d8, 298 K): δ
44.0 (s). 13C{1H} APT NMR plus HSQC and HMBC (75.47 MHz,
toluene-d8, 253 K): δ 145.4 (s, NCHN), 140.5 (s, OsNCH), 119.4 (s,
CHNCH3), 31.4 (s, CH3) 27.1 (vt, N = 22.1, PCH(CH3)2), 20.2 (s,
PCH(CH3)2).
Preparation of OsH3{CNHCHCHNCHdC(Ph)O}(PiPr3)2
jj
j
(6). A solution of 4 (100 mg, 0.14 mmol) in toluene was heated under
reflux for 17 h. During this time the solution changed from colorless to
dark green. After it was cooled room temperature, the resulting solution
was filtered through Celite and the solvent was removed. Pentane was
added at 223 K to the residue to afford a green solid, which was washed
1
with further portions of pentane and dried in vacuo. H and 31P{1H}
NMR spectra show that the reaction is quantitative, but the obtained
yield is very low due to the high solubility of the complex in pentane.
Yield: 45 mg (33%). Anal. Calcd for C29H54N2OOsP2: C, 49.83; H,
7.78; N, 4.01. Found: C, 49.71; H, 7.89; N, 4.23. IR (cm-1): ν(NH)
3120 (w), ν(OsH) 2111 (w). 1H NMR (400 MHz, C6D6, 298 K): δ 8.04
(d, JH-H = 7.5, o-Ph), 7.68 (br, 1H, NH), 7.29 (t, JH-H = 7.5, 2H, m-Ph),
7.13 (m, 1H, p-Ph), 6.33 (s, 1H, dCH), 6.22 (dd, JH-H = JH-H = 2, 1H,
CH im), 6.01 (dd, JH-H = JH-H = 2, 1H, CH im), 2.00 (m, 6H,
PCH(CH3)2), 1.22 (dvt, JH-H = 6.8, N = 12.8, 18H, PCH(CH3)2),
1.06 (dvt, JH-H = 6.8, N = 12, 18H, PCH(CH3)2), -11.3 (br, 3H, Os-
H). 1H{31P} NMR (400 MHz, CDCl2F, 139 K, high-field region): δ -
5.0 (br t, JH-H = 20, 1H, Os-H), -14.5 (br, 2H, Os-H). 31P{1H}
NMR (161.9 MHz, C6D6, 298 K): δ 31.5 (s). 13C{1H} APT NMR plus
HSQC (75 MHz, C6D6, 298 K): δ 169.2 (t, JP-C = 7.8, NCN), 151.5 (s,
CO), 142.5 (s, Cipso), 126.6, 125.6, 125.3 (all s, Ph), 116.9, 115.8 (both s,
CH im), 97.2 (s, dCH), 26.9 (vt, N = 23, PCH(CH3)2), 20.5 and 19.7
(both s, PCH(CH3)2).
Preparation of OsH4[PhCH(OH)CH2Im](PiPr3)2 (4). A color-
less solution of 1 (100 mg, 0.19 mmol) in THF (10 mL) was treated with
1.2 equiv of 1-(2-hydroxy-2-phenylethyl)imidazole (45.7 mg, 0.23
mmol) and the mixture heated under reflux for 17 h. The resulting
solution was cooled to room temperature, filtered through Celite, and
taken to dryness. Addition of methanol to the residue at 223 K afforded a
white solid that was washed with methanol and dried in vacuo. Yield: 101
mg (74%). Anal. Calcd for C29H58N2OOsP2: C, 49.54; H, 8.32; N, 3.98.
Found: C, 49.32; H, 8.45; N, 4.10. IR (cm-1): ν(OsH) 2108 (w),
ν(CdN) 1775 (s). 1H NMR (500 MHz, C6D6, 298 K): δ 7.73 (s, 1H,
CH im), 7.25 (s, 1H, CH im), 7.14-6.96 (m, 5H, Ph), 5.79 (s, 1H, CH
im), 4.71 (br, 1H, -OH), 4.16 (t, JH-H = 5.2, 1H, CH(OH)Ph), 3.19
Preparation of OsH3{CNHCHCHNCHdC(CH3)O}(PiPr3)2
jj
j
(7). A solution of 5 (100 mg, 0.16 mmol) in toluene was heated under
reflux for 15 h. During this time the solution changed from colorless to
dark green. After it was cooled to room temperature, the resulting
solution was filtered through Celite and the solvent was removed in
1663
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
vacuo. Pentane was added to the residue to afford a green solid that was
washed with pentane (2 ꢁ 2 mL) and dried in vacuo. Yield: 95 mg
(52%). Anal. Calcd for C24H52N2OOsP2: C, 45.26; H, 8.23; N, 4.39.
Found: C, 44.91; H, 7.98; N, 4.21. IR (cm-1): ν(N-H) 3132, ν(Os-
H) 2120. 1H NMR (300 MHz, C6D6, 298 K): δ 7.64 (br, 1H, NH), 6.12
(dd, JH-H = JH-H = 2, 1H, CH im), 5.99 (dd, JH-H = JH-H = 2, 1H, CH
im), 5.47 (s, 1H, dCH), 2.03 (m, 6H, PCH(CH3)2), 1.85 (s, 3H,
-CH3), 1.25 (dvt, JH-H = 6.9, N = 12.6, 18H, PCH(CH3)2), 1.10 (dvt,
JH-H = 6.9, N = 12, 18H, PCH(CH3)2), -11.24 (br, 3H, OsH).
1H{31P} NMR (400 MHz, CDCl2F, 143 K, high-field region): δ -5.5
(d, JH-H = 25, 1H, Os-H), -14.4 (dd, JH-H = 25, JH-H = 72, 1H, Os-
H), -16.9 (d, JH-H = 72, 1H, Os-H). 31P{1H} NMR (121.4 MHz,
C6D6, 298 K): δ 31.4 (s). 13C{1H} APT NMR plus HSQC and HMBC
(75.47 MHz, C6D6, 298 K): δ 167.4 (t, JP-C = 7.9, NCN), 152.3 (s, CO),
116.1, 115.5 (both s, CH im), 95.5 (s, dCH), 27.1 (vt, N = 22.6,
PCH(CH3)2), 23.7 (s, CH3), 20.4 and 19.7 (both s, PCH(CH3)2).
and stirred for 30 min at room temperature. The resulting suspension
was filtered through Celite and was taken to dryness. Addition of
pentane afforded a green solid (73 mg, 80% yield) that was identified
as 6 by 1H and 31P{1H} NMR spectroscopy.
Reaction of 9 with KtBuO. A brown solution of 9 (100 mg, 0.138
mmol) in THF was treated with 2 equiv of KtBuO (31 mg, 0.28 mmol)
and stirred for 30 min at room temperature. The resulting suspension
was filtered through Celite and was taken to dryness. Addition of
pentane afforded a green solid (72 mg, 82% yield) that was identified
as 7 by 1H and 31P{1H} NMR spectroscopy.
Preparation of [OsH3{CN(CH2Ph)CHCHNCH2C(Ph)=O}
jj
j
(PiPr3)2]BF4 (10). A colorless solution of 1 (100 mg, 0.19 mmol) in THF
(10 mL) was treated with 1.2 equiv of 3-benzyl-1-(2-hydroxy-2-pheny-
lethyl)imidazolium tetrafluoroborate and heated at reflux temperature for
29 h. During this time the solution changed from colorless to garnet. After the
mixture was cooled to room temperature, it was filtered through Celite and
the solvent removed in vacuo. Subsequent addition of diethyl ether to the
residue afforded a garnet solid, which was washed with diethyl ether (2 ꢁ
3 mL) and dried in vacuo. Yield: 104 mg (61%). Anal. Calcd for
C36H61BF4N2OOsP2: C, 49.31; H, 7.01; N, 3.19. Found: C, 48.96; H,
6.85; N, 3.34. IR (cm-1): ν(OsH) 2158 (w), ν(CdO) 1593 (m), ν(BF4)
1038 (s). 1H NMR (400 MHz, CD2Cl2, 298 K): δ 8.15 (d, JH-H = 7.3, 2H,
o-Ph), 7.77 (t, JH-H =7.3, 1H, p-Ph), 7.60 (m, 3H, m-Ph and CH im), 7.35-
7.23(m, 5H, Ph), 7.16(d, JH-H =1.5, 1H, CHim), 6.07(s, 2H, CH2COPh),
5.39 (s, 2H, CH2Ph), 1.75 (m, 6H, PCH(CH3)2), 1.01 (dvt, JH-H = 6.9, N =
13.2, 18H, PCH(CH3)2), 0.98 (dvt, JH-H = 6.6, N = 12.6, 18H, PCH-
(CH3)2), -10.9 (br, 3H, OsH). 1H{31P} NMR (400 MHz, CDCl2F, 189 K,
high-field region): δ -6.7 (br, 1H, Os-H), -9.6 (br, 1H, Os-H), -16.5
(t, JH-H = 36, 1H, Os-H). 31P{1H} NMR (121.5 MHz, CD2Cl2, 298 K): δ
30.2 (s). 13C{1H} APT NMR plus HSQC and HMBC (75.47 MHz,
CD2Cl2, 298 K): δ 196.7 (t, JP-C = 1.5, CO), 183.5 (t, JP-C = 6.3, NCN),
136.1 (s, CH Ph), 135.8 and 133.9 (both s, Cipso Ph), 130.1, 129.4, 129.3,
128.7, 128.2 (all s, CH Ph), 124.0 (s, CH im), 123.1 (s, CH im), 55.8 (s,
CH2Ph), 55.0 (s, CH2COPh), 27.1 (vt, N = 25.3, PCH(CH3)2), 19.9 and
19.7 (both s, PCH(CH3)2).
Preparation of [OsH3{CNHCHCHNCH2C(Ph)dO}(PiPr3)2]
jj
j
BF4 (8). A solution of 6 (50 mg, 0.07 mmol) in diethyl ether (5 mL) was
treated with 1 equiv of HBF4 OEt2 (9.8 μL, 0.07 mmol) and stirred for 15
3
min at room temperature. During the course of the reaction a brown solid
formed. The solvent was removed, and the solid was washed with further
portions of diethyl ether (2 ꢁ 2 mL) and dried in vacuo. Yield: 42 mg
(56%). Anal. Calcd for C29H55BF4N2OOsP2: C, 44.27; H, 7.04; N, 3.56.
Found: C, 44.58; H, 7.32; N, 3.45. IR (cm-1): ν(N-H) 3145 (w),
1
ν(Os-H) 2151 (w), ν(CdO) 1593 (m), ν(BF4) 1023 (s). H NMR
(400 MHz, CD2Cl2, 298 K): δ 9.50 (br, 1H, NH), 8.09 (d, JH-H = 7.2,
2H, o-Ph), 7.76 (t, JH-H = 7.5, 1H, p-Ph), 7.59 (t, JH-H = 7.5, 2H, m-Ph),
7.34 (dd, JH-H = JH-H = 2.0, 1H, CH im), 7.25 (dd, JH-H = JH-H = 2.0,
1H, CH im), 6.15 (t, JH-P = 2, 2H, CH2), 1.93 (m, 6H, PCH(CH3)2),
1.04 (dvt, JH-H = 6.9, N = 13, 18H, PCH(CH3)2), 1.03 (dvt, JH-H = 6.9,
N = 13, 18H, PCH(CH3)2), -10.5 (very br, 3H, Os-H). 1H{31P} NMR
(300 MHz, CD2Cl2, 189 K, high-field region): δ -7.6 (br, 1H, Os-
H), -8.1 (br, 1H, Os-H), -16.5 (t, JH-H = 16, 1H, Os-H). 31P{1H}
NMR (161.9 MHz, CD2Cl2, 298 K): δ 29.3 (s). 13C{1H} APT NMR plus
HSQC and HMBC (125.75 MHz, CD2Cl2, 298 K): δ 192.0 (CO), 176.1
(t, JP-C = 6.8, NCN), 135.0 (s, CH Ph), 133.2 (s, Cipso Ph), 129.2, 127.8
(both s, CH Ph), 121.1 (s, CH im), 119.5 (s, CH im), 53.7 (s, CH2), 26.7
(vt, N = 25.5, PCH(CH3)2), 19.1 and 18.6 (both s, PCH(CH3)2).
Preparation of [OsH3{CN(CH2Ph)CHCHNCH2C(CH3)dO}
jj
j
(PiPr3)2]BPh4 (11). A colorless solution of 1 (125 mg, 0.24 mmol) in
THF (10 mL) was treated with 1.2 equiv of 3-benzyl-1-(2-hydroxypro-
pyl)imidazolium tetraphenylborate (131.0 mg, 0.29 mmol) and heated
under reflux during 29 h. During this time the solution changed from
colorless to yellow. After the mixture was cooled to room temperature, it
was filtered through Celite and taken to dryness. Subsequent addition of
diethyl ether to the residue afforded a yellow solid, which was washed
with diethyl ether (2 ꢁ 3 mL) and dried in vacuo. Yield: 227 mg (90%).
Anal. Calcd for C55H79BN2OOsP2: C, 63.08; H, 7.60; N, 2.67.
Preparation of [OsH3{CNHCHCHNCH2C(CH3)dO}(PiPr3)2
jj
j
]BF4 (9). A solution of 7 (100 mg, 0.16 mmol) in THF (5 mL) was treated
with 1 equiv of HBF4 OEt2 (21 μL, 0.16 mmol). The resulting solution
3
was stirred at room temperature for 15 min. During this time the solution
changed from green to dark brown. The solvent was removed, and diethyl
ether was added to afford a brown solid, which was washed with further
portions of diethyl ether and dried in vacuo. Yield: 96 mg (90%). Anal. Calcd
for C24H53BF4N2OOsP2: C, 39.78; H, 7.37; N, 3.86. Found: C, 40.07; H,
6.94; N, 3.93. IR (cm-1): ν(NH) 3358, ν(OsH) 2158 (w), ν(CdO) 1584
(m), ν(BF4) 1023 (s). 1H NMR (300 MHz, CD2Cl2, 298 K): δ 9.61 (br s,
1H, N-H), 7.19 (s, 1H, CH im), 7.04 (s, 1H, CH im), 5.62 (s, 2H, CH2),
1.85 (m, 6H, PCH(CH3)2), 1.02 (dvt, JH-H = 6.8, N = 16, 18H, PCH-
(CH3)2)), 0.99 1.06 (dvt, JH-H = 6.8, N = 15, 18H, PCH(CH3)2), -11.1
(very br, 3H, Os-H). 1H{31P} NMR (300 MHz, CD2Cl2, 189 K, high-field
1
Found: C, 63.41; H, 7.44; N, 2.80. IR (cm-1): ν(OsH) 2157. H
NMR (400 MHz, CD2Cl2, 298 K): δ 7.49 (br, 8H, o-BPh4), 7.41-
7.23 (m, 5H, Ph), 7.06 (t, JH-H = 7.4, 8H, m-BPh4), 6.93 (d, JH-H
=
2, 1H, CH im), 6.90 (t, JH-H = 7.2, 4H, p-BPh4), 6.41 (d, JH-H = 2,
1H, CH im), 5.28 (s, 2H, CH2Ph), 3.87 (s, 2H, CH2COCH3), 1.82
(s, 3H, CH3), 1.73 (m, 6H, PCH(CH3)2), 0.99 (dvt, JH-H = 6.9, N =
13, 18H, PCH(CH3)2), 0.98 (dvt, JH-H = 6.9, N = 13, 18H, PCH(CH3)2),
-11.4 (br, 3H, OsH). 1H{31P} NMR (300 MHz, CDCl2F, 189 K, high-field
region): δ -7.8 (br, 1H, Os-H), -8.6 (br, 1H, Os-H), -17.0 (t, JH-H
=
20, 1H, Os-H). 31P{1H} NMR (121.5 MHz, CD2Cl2, 298 K): δ 29.2 (s).
13C{1H} APT NMR plus HSQC (75.47 MHz, CD2Cl2, 263 K): δ 206.0
(CO), 176.3 (t, JP-C = 7.1, NCN), 120.6 (s, CH im), 120.1 (s, CH im), 57.6
(s, CH2), 29.6 (s, CH3), 27.2 (vt, N = 25.7, PCH(CH3)2), 19.5 and 19.0
(both s, PCH(CH3)2).
region): δ -7.4 (br, 1H, Os-H), -9.9 (br, 1H, Os-H), -17.1 (t, JH-H
=
39, 1H, Os-H). 31P{1H} NMR (161.9 MHz, CD2Cl2, 298 K): δ 29.4 (s).
13C{1H} APT NMR plus HSQC and HMBC (100.63 MHz, CD2Cl2, 298
K): δ 206.7 (s, CO), 181.9 (t, JP-C = 6, NCN), 163.9 (q, JB-C= 49.2, Cipso
BPh4), 135.6 (q, JB-C = 1.2, o-CH BPh4), 125.2 (q, JB-C = 2.6, m-CH
BPh4), 122.8 (s, CH im), 121.7 (s, p-CH BPh4), 120.5 (s, CH im), 56.6 (s,
Reaction of 8 with KtBuO. A brown solution of 8 (100 mg, 0.127
mmol) in THF was treated with 2 equiv of KtBuO (28 mg, 0.253 mmol)
1664
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
CH2COCH3), 55.2 (s, CH2Ph), 29.0 (s, CH3), 26.3 (vt, N = 25.2,
PCH(CH3)2), 19.1 and 19.0 (both s, PCH(CH3)2).
hydrogen atoms were observed or calculated and refined freely or
refined with a restricted riding model. Hydride ligands were observed
in the difference Fourier maps and refined with restrained Os-H bond
lengths (1.59(1) Å, CSD). Two methyl groups (C25 and C26) of one of
the triisopropylphosphine ligands of complex 6 were refined in two
positions (0.7/0.3). These methyl groups were refined with an isotropic
model and restrained geometry. For 6 0.25 molecule of pentane was
observed in the asymmetric unit as crystallization solvent. For 10, 0.25
(diethyl ether) and 0.5 (dichloromethane, disordered) molecules were
observed in the asymmetric unit as crystallization solvents. They were
refined with restrained geometry, with isotropic atoms, and without
hydrogens. All the highest electronic residuals were observed in the close
proximity of the Os centers and make no chemical sense.
Crystal Data for 2:. C30H60N2OsP2, Mw = 700.94, colorless, prism
(0.20 ꢁ 0.12 ꢁ 0.10), monoclinic, space group P21/n, a = 12.2220(16)
Å, b = 15.4235(19) Å, c = 17.219(2) Å, R = 90.00°, β = 98.900(2)°, γ =
90.00 o, V = 3206.8(7) Å3, Z = 4, Dcalcd = 1.452 g cm-3, F(000) = 1440,
T = 100(2) K, μ = 4.096 mm-1, 39 565 measuredreflections (2θ = 3-58°,
ω scans 0.3°), 7856 unique reflections (Rint = 0.0785); minimum/
maximum transmission factors 0.504/0.659, final agreement factors
R1 = 0.0384 (5176 observed reflections, I > 2σ(I)) and wR2 =
0.0556, 7856/5/354 data/restraints/parameters, GOF = 0.740, largest
peak and hole 1.114 and -1.241 e/Å3.
Preparation of OsH3{CN(CH2Ph)CHCHNCHdC(Ph)O}
jj
j
(PiPr3)2 (12). A solution of 10 (100 mg, 0.11 mmol) in THF (5 mL)
was treated with 2 equiv of KtBuO (25 mg, 0.22 mmol). After the
mixture was stirred for 40 min at room temperature, it changed from
orange to green. The resulting suspension was filtered through Celite,
and the resulting solution was taken to dryness, affording a yellow solid
that was washed with pentane and dried in vacuo. Yield: 41 mg (46%).
Anal. Calcd for C36H60N2OOsP2: C, 54.79; H, 7.66; N, 3.44. Found: C,
54.42; H, 7.83; N, 3.21. IR (cm-1): ν(Os-H) 2120 (w), ν(CdN) 1865.
1H NMR (300 MHz, C6D6, 298 K): δ 8.04 (d, JH-H = 7.5, 2H, Ph), 7.29
(t, JH-H = 7.5, 2H, Ph), 7.11 (m, 6H, Ph), 6.44 (d, JH-H = 1.8, 1H, CH
im), 6.41 (d, JH-H = 1.8, 1H, CH im), 6.40 (s, dCH), 5.31 (s, 2H, CH2),
1.96 (m, 6H, PCH(CH3)2), 1.23 (dvt, JH-H = 6.7, N = 13, 18H,
PCH(CH3)2), 1.00 (dvt, JH-H = 6.5, N = 12, 18H, PCH(CH3)2), -11.3
(br, 3H, OsH). 1H{31P} NMR (400 MHz, CDCl2F, 138 K, high-field
region): δ -5.4 (br, 1H, Os-H), -14.6 (br, 1H, Os-H), -15.2 (br,
1H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 298 K): δ 32.7 (s).
13C{1H} APT NMR plus HSQC and HMBC (75.47 MHz, C6D6, 298
K): δ 175.1 (t, JP-C = 7.5, NCN), 151.4 (s, CO), 142.2 and 137.3 (both
s, Cipso Ph), 128.8, 128.3, 127.9, 126.6, 125.2 (all s, CH Ph), 119.7 (s, CH
im), 118.3 (s, CH im), 97.9 (s, dCH), 55.2 (s, -CH2-), 26.12 (vt, N =
22.7, PCH(CH3)2), 20.3 and 19.9 (both s, PCH(CH3)2).
Crystal Data for 6:. C29H54N2OOsP2 0.25C5H12, Mw = 716.92,
3
brown, prism (0.14 ꢁ 0.03 ꢁ 0.03), tetragonal, space group I41/a, a =
35.231(9) Å, b = 35.231(9) Å, c = 11.818(4) Å, R = 90.00°, β = 90.00°,
γ = 90.00o, V = 14669(7) Å3, Z = 16, Dcalcd = 1.298 g cm-3, F(000) =
5864, T = 100(2) K, μ = 3.586 mm-1. 47 362 measured reflections (2θ: =
3-58°, ω scans 0.3°), 9055 unique reflections (Rint = 0.1108), minimum/
maximum transmission factors 0.694/0.801, final agreement factors R1 =
0.0398 (4622 observed reflections, I>2σ(I)) and wR2 = 0.0810, 9055/23/
368 data/restraints/parameters, GOF = 0.803, largest peak and hole 0.864
and -0.878 e/Å3.
Preparation of OsH3{CN(CH2Ph)CHCHNCHdC(CH3)O}
jj
j
(PiPr3)2 (13). A yellow solution of 11 (120 mg, 0.12 mmol) in THF
was treated with 2 equiv of KtBuO (27 mg, 0.24 mmol) and stirred for 40
min at room temperature. The resulting suspension was filtered through
Celite and was taken to dryness. Addition of pentane to the residue
afforded a yellow solid that was washed with pentane and dried in vacuo.
Yield: 34 mg (41%). Anal. Calcd for C31H58N2OOsP2: C, 51.22; H,
8.04; N, 3.85. Found: C, 50.85; H, 8.32; N, 3.64. IR (cm-1): ν(OsH)
2115. 1H NMR (300 MHz, C6D6, 298 K): δ 7.09-6.98 (m, 5H, Ph),
6.37 (d, JH-H = 1.8, 1H, CH im), 6.31 (d, JH-H = 1.8, 1H, CH im), 5.52
(s, 1H, CH), 5.29 (s, 2H, CH2), 1.98 (m, 6H, PCH(CH3)2), 1.90
(s, CH3), 1.26 (dvt, JH-H = 6.8, N = 12.9, 18H, PCH(CH3)2), 1.05 (dvt,
JH-H = 6.8, N = 12, 18H, PCH(CH3)2), -11.4 (br, 3H, OsH). 1H{31P}
NMR (300 MHz, CDCl2F, 172 K, high-field region): δ -5.7 (br, 1H,
Os-H), -15.0 (AB spin system, JA-B = 288, Δν = 684, 2H, Os-H).
31P{1H} NMR (161.9 MHz, C6D6, 298 K): δ 32.3 (s). 13C{1H}- APT
NMR plus HSQC and HMBC (75.47 MHz, C6D6, 298 K): δ 173.8
(t, JP-C = 7.5, NCN), 152.4 (s, CO), 137.6 (s, Cipso Ph), 128.7, 128.3
(both s, CH Ph), 119.3, 117.6 (both s, CH im), 96.1 (s, CH), 55.1 (s,
CH2), 26.5 (vt, N = 22, PCH(CH3)2), 23.4 (s, CH3), 20.1 and 20.0 (both
s, PCH(CH3)2).
Crystal Data for 10:. C36H61BF4N2OOsP2 0.25C4H10O 0.5CH2
3
3
Cl2, Mw = 937.81, orange, irregular block (0.10 ꢁ 0.10 ꢁ 0.08), triclinic,
space group P1, a = 11.352(3) Å, b = 13.480(4) Å, c = 15.209(4) Å, R =
75.175(5)o, β = 80.377(5)°, γ = 74.714(4)o, V = 2157.8(11) Å3, Z = 2,
Dcalcd = 1.443 g cm-3, F(000) = 955, T = 100(2) K, μ = 3.139 mm-1
,
27 164 measured reflections (2θ = 4-58°, ω scans 0.3°), 10 376
unique reflections (Rint = 0.0447), minimum/maximum transmission
factors 0.700/0.803, final agreement factors R1 = 0.0310 (8227
observed reflections, I > 2σ(I)) and wR2 = 0.0595, 10 376/25/512
data/restraints/parameters, GOF = 0.845, largest peak and hole 1.097
and -0.974 e/Å3.
Computational Details. The calculations have been carried out
using the Gaussian 03 computational package.42 The structures have
been optimized using DFT and the B3LYP functional. The 6-31G**
basis set has been used for all atoms except for Os, where the LANL2DZ
basis and pseudopotential have been used instead.
Structural Analysis of Complexes 2, 6, and 10. Crystals
suitable for X-ray diffraction were obtained by slow diffusion of
methanol into a solution of complex 2 in dichloromethane, by cooling
a solution of complex 6 to -20 °C, and by slow diffusion of diethyl ether
into a solution of complex 10 in dichloromethane. X-ray data for all
complexes were collected on a Bruker Smart APEX CCD diffractometer
equipped with a normal-focus, 2.4 kW sealed-tube source (Mo radiation,
λ = 0.710 73 Å) operating at 50 kV and 30 mA (2) or 40 mA (6, 10).
Data were collected over the complete sphere by a combination of four
sets. Each frame exposure time was 10 s (2, 10) or 50 s (6) covering 0.3°
in ω. Data were corrected for absorption by using a multiscan method
applied with the SADABS program.40 The structures of all compounds
were solved by the Patterson method. Refinement, by full-matrix least
squares on F2 with SHELXL97,41 was similar for all complexes, including
isotropic and subsequently anisotropic displacement parameters. The
’ ASSOCIATED CONTENT
S
Supporting Information. Tables, text, and CIF files
b
giving details of the X-ray analysis and crystal structure determi-
nation, including bond lengths and angles of compounds 2, 6,
and 10, orthogonal coordinates of the optimized theoretical
structures, and the full ref 42. This material is available free of
charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: maester@unizar.es (M.A.E.).
1665
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
’ ACKNOWLEDGMENT
Pons, V.; Stevens, E. D.; Heinekey, D. M.; Nolan, S. P. Angew. Chem., Int.
Ed. 2005, 44, 2512. (f) Corberꢀan, R.; Sanaꢀu, M.; Peris, E. Organometallics
2006, 25, 4002. (g) Hanasaka, F.; Tanabe, Y.; Fujita, K.; Yamaguchi, R.
Organometallics 2006, 25, 826. (h) Spencer, L. P.; Beddie, C.; Hall, M. B.;
Fryzuk, M. D. J. Am. Chem. Soc. 2006, 128, 12531. (i) Corberꢀan, R.;
Sanaꢀu, M.; Peris, E. J. Am. Chem. Soc. 2006, 128, 3974. (j) Cariou, R.;
Fischmeister, C.; Toupet, L.; Dixneuf, P. H. Organometallics 2006,
25, 2126. (k) Tanabe, Y.; Hanasaka, F.; Fujita, K.; Yamaguchi, R.
Organometallics 2007, 26, 4618. (l) Hong, S. H.; Chlenov, A.; Day,
M. W.; Grubbs, R. H. Angew. Chem., Int. Ed. 2007, 46, 5148.
(m) Ellul, C. E.; Mahon, M. F.; Saker, O.; Whittlesey, M. K. Angew.
Chem., Int. Ed. 2007, 46, 6343.
(15) (a) Jazzar, R. F. R.; Macgregor, S. A.; Mahon, M. F.;
Richards, S. P.; Whittlesey, M. K. J. Am. Chem. Soc. 2002, 124,
4944. (b) Diggle, R. A.; Macgregor, S. A.; Whittlesey, M. K. Organo-
metallics 2008, 27, 617. (c) Bola~no, T.; Buil, M. L.; Esteruelas, M. A.;
Izquierdo, S.; Lalrempuia, R.; Olivꢀan, M.; O~nate, E. Organometallics
2010, 29, 4517.
Financial support from the MICINN of Spain (Project
Nos. CTQ2007-65218, CTQ2008-00810, and Consolider
Ingenio 2010 CSD2007-00006), the Diputaciꢀon General de
Aragꢀon (E35), the Generalitat Valenciana (PROMETEO/
2009/0349 and FEDER), and the European Social Fund is
acknowledged.
DEDICATION
†Dedicated to Prof. Kenneth G. Caulton on the occasion of this
70th birthday.
’ REFERENCES
(1) (a) Arduengo, A. J., III Acc. Chem. Res. 1999, 32, 913. (b) Hahn,
F. E.; Jahnke, M. C. Angew. Chem., Int. Ed. 2008, 47, 3122. (c) Schuster,
O.; Yang, Li.; Raubenheimer, H. G.; Albrecht, M. Chem. Rev. 2009,
109, 3445. (d) de Frꢀemont, P.; Marion, N.; Nolan, S. P. Coord. Chem.
Rev. 2009, 253, 862.
(16) (a) Herrmann, W. A.; Goossen, L. J.; Spiegler, M. J. Organomet.
Chem. 1997, 547, 357. (b) McGuinness, D. S.; Cavell, K. J. Organome-
tallics 2000, 19, 741.
(17) (a) Gr€undemann, S.; Kovacevic, A.; Albrecht, M.; Faller,
J. W.; Crabtree, R. H. Chem. Commun. 2001, 2274. (b) Kovacevic, A.;
Gr€undemann, S.; Miecznikowski, J. R.; Clot, E.; Eisenstein, O.; Crabtree,
R. H. Chem. Commun. 2002, 2580. (c) Gr€undemann, S.; Kovacevic, A.;
Albrecht, M.; Faller, J. W.; Crabtree, R. H. J. Am. Chem. Soc. 2002,
124, 10473. (d) Crabtree, R. H. Pure Appl. Chem. 2003, 75, 435. (e)
Appelhans, L. N.; Zuccaccia, D.; Kovacevic, A.; Chianese, A. R.;
Miecznikowski, J. R.; Macchioni, A.; Clot, E.; Eisenstein, O.; Crabtree,
R. H. J. Am. Chem. Soc. 2005, 127, 16299. (f) Baya, M.; Eguillor, B.;
Esteruelas, M. A.; Olivꢀan, M.; O~nate, E. Organometallics 2007, 26, 6556.
(18) (a) Wang, R.; Zeng, Z.; Twamley, B.; Piekarski, M. M; Shreeve,
J. M. Eur. J. Org. Chem. 2007, 655. (b) Lee, H. M.; Chiu, P. L.; Hu, C.-H.;
Lai, C.-L.; Chou, Y.-C. J. Organomet. Chem. 2005, 690, 403.
(2) (a) Kantchev, E. A. B; O'Brien, C. J.; Organ, M. G. Angew. Chem.,
Int. Ed. 2007, 46, 2768. (b) Marion, N.; Nolan, S. P. Acc. Chem. Res.
2008, 41, 140. (c) Samojzowicz, C.; Bieniek, M.; Grela, K. Chem. Rev.
2009, 109, 3708. (d) Díez-Gonzꢀalez, S.; Marion, N.; Nolan, S. P. Chem.
Rev. 2009, 109, 3612.
(3) Hindi, K. M.; Panzner, M. J.; Tessier, C. A.; Cannon, C. L.;
Youngs, W. J. Chem. Rev. 2009, 109, 3859.
(4) Mercs, L.; Albrecht, M. Chem. Soc. Rev. 2010, 39, 1903.
(5) Other methods used are also the insertion of a metal into the
CdC bond of bis(imidazolin-2-ylidene)-based electron-rich olefins and
the oxidative addition of an imidazolium cation by activation of a C-X
(X = H, I, Me) bond at low-valent or metal hydride precursors. See:
Arnold, P. L.; Pearson, S. Coord. Chem. Rev. 2007, 251, 596.
(6) (a) Hahn, F. E.; Holtgrewe, C.; Pape, T.; Martín, M.; Sola, E.;
Oro, L. A. Organometallics 2005, 24, 2203. (b) Burling, S.; Mahon, M. F.;
Reade, S. P.; Whittlesey, M. K. Organometallics 2006, 25, 3761.
(7) Huynh, H. V.; Holtgrewe, C.; Pape, T.; Koh, L. L.; Hahn, E.
Organometallics 2006, 25, 245.
(8) (a) Peris, E.; Loch, J. A.; Mata, J.; Crabtree, R. H. Chem. Commun.
2001, 201. (b) Schwarz, J.; B€ohm, V. P. W.; Gardiner, M. G.; Grosche,
M.; Herrmann, W. A.; Hieringer, W.; Raudaschl-Sieber, G. Chem. Eur. J.
2006, 6, 1773.
(9) Muehlhofer, M.; Strassner, T.; Herdyweck, E.; Herrmann, W. A.
J. Organomet. Chem. 2002, 660, 121.
(10) Crudden, C. M.; Allen, D. P. Coord. Chem. Rev. 2004, 248, 2247.
(11) (a) Danopoulos, A. A.; Tsoureas, N.; Green, J. C.; Hursthouse,
M. B. Chem. Commun. 2003, 756. (b) Hu, X.; Meyer, K. J. Am. Chem. Soc.
2004, 126, 16322. (c) Galan, B. R.; Gembicky, M.; Dominiak, P. M.;
Keister, J. B.; Diver, S. T. J. Am. Chem. Soc. 2005, 127, 15702. (d) Becker,
E.; Stingl, V.; Dazinger, G.; Puchberger, M.; Mereiter, K.; Kirchner, K. J.
Am. Chem. Soc. 2006, 128, 6572. (e) Becker, E.; Stingl, V.; Dazinger, G;
Mereiter, K.; Kirchner, K. Organometallics 2007, 26, 1531. (f) Fantasia,
S.; Jacobsen, H.; Cavallo, L.; Nolan, S. P. Organometallics 2007, 26,
3286.
(12) (a) Caddick, S.; Cloke, F. G. N.; Hitchcock, P. B.; Lewis, A. K de
K. Angew. Chem., Int. Ed. 2004, 43, 5824. (b) Burling, S.; Mahon, M. F.;
Powell, R. E.; Whittlesey, M. K.; Williams, J. M. J. J. Am. Chem. Soc. 2006,
128, 13702.
(13) Waltman, A. W. W.; Ritter, T.; Grubbs, R. H. Organometallics
2006, 25, 4238.
(19) (a) Arnold, P. L.; Mungur, S. A.; Blake, A. J.; Wilson, C. Angew.
Chem., Int. Ed. 2003, 42, 5981. (b) Spencer, L. P.; Winston, S.; Fryzuk,
M. D. Organometallics 2004, 23, 3372. (c) Spencer, L. P.; Fryzuk, M. D.
J. Organomet. Chem. 2005, 690, 5788.
(20) Yang, C.; Lee, H. M.; Nolan, S. P. Org. Lett. 2001, 3, 1511. (b)
Lee, H. M.; Chiu, P. L.; Zeng, J. Y. Inorg. Chim. Acta 2004, 357, 4313.
(21) Torregrosa, R.; Pastor, I.; Yus, M. Tetrahedron 2007, 63, 469.
(22) (a) Arnold, P. L.; Scarisbrick, A. C; Blake, A. J.; Wilson, C.
Chem. Commun. 2001, 2340. (b) Arnold, P. L.; Rodden, M.; Davis,
K. M.; Scarisbrick, A. C; Blake, A. J.; Wilson, C. Chem. Commun.
2004, 1612. (c) Waltman, A. W.; Grubbs, R. H. Organometallics 2004,
23, 3105. (d) Ketz, B. E.; Ottenwaelder, X. G.; Waymouth, R. M. Chem.
Commun. 2005, 5693. (e) Arnold, P. L.; Blake, A. J.; Wilson, C. Chem.
Eur. J. 2005, 11, 6095. (f) Boydston, A. J.; Rice, J. D.; Sanderson, M. D.;
Dykhno, O. L.; Bielawski, C. W. Organometallics 2006, 25, 6087. (g)
Waltman, A. W.; Ritter, T.; Grubbs, R. H. Organometallics 2006,
25, 4238. (h) Patel, D.; Liddle, S. T.; Mungur, S. A.; Rodden, M.; Blake,
A. J.; Arnold, P. L. Chem. Commun. 2006, 1124. (i) Jones, N. A.; Liddle,
S. T.; Wilson, C.; Arnold, P. L. Organometallics 2007, 26, 755. (j) Ren,
H.; Yao, P.; Xu, S.; Song, H.; Wang, B. J. Organomet. Chem. 2007,
692, 2092. (k) Arnold, P. L.; Zlatogorsky, S.; Jones, N. A.; Carmichael,
C. D.; Liddle, S. T.; Blake, A. J.; Wilson, C. Inorg. Chem. 2008, 47, 9042.
(23) (a) Sundberg, R. J.; Bryan, R. F.; Taylor, I. F., Jr.; Taube, H. J. Am.
Chem. Soc. 1974, 96, 381. (b) Michelin, R. A.; Zanotto, L.; Braga, D.;
Sabatino, P.; Angelici, R. J. Inorg. Chem. 1988, 27, 93. (c) Tan, K. L.;
Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2002, 124, 3202. (d) Lewis,
J. C.; Wiedemann, S. H.; Bergman, R. G.; Ellman, J. A. Org. Lett. 2004,
6, 35. (e) Wang, X.; Chen, H.; Li, X. Organometallics 2007, 26, 4684. (f)
Ruiz, J.; Perandones, B. F. J. Am. Chem. Soc. 2007, 129, 9298. (g) Ruiz, J.;
Perandones, B. F.; García, G.; Mosquera, M. E. G. Organometallics 2007,
26, 5687. (h) Miranda-Soto, V.; Grotjahn, D. B.; DiPasquale, A. G.;
Rheingold, A. L. J. Am. Chem. Soc. 2008, 130, 13200. (i) Araki, K.; Kuwata,
S.; Ikariya, T. Organometallics 2008, 27, 2176. (j) Huertos, M. A.; Pꢀerez, J.;
Riera, L.; Menꢀendez-Velꢀazquez, A. J. Am. Chem. Soc. 2008, 130, 13530.
(14) See for example: (a) Burling, S.; Mahon, M. F.; Paine, B. M.;
Whittlesey, M. K.; Williams, J. M. J. Organometallics 2004, 23, 4537. (b)
Dorta, R.; Stevens, E. D.; Nolan, S. P. J. Am. Chem. Soc. 2004, 126, 5054.
(c) Abdur-Rashid, K.; Fedorkiw, T.; Lough, A. J.; Morris, R. H.
Organometallics 2004, 23, 86. (d) Cabeza, J. A.; del Río, I.; Miguel, D.;
Sꢀanchez-Vega, M. G. Chem. Commun. 2005, 3956. (e) Scott, N. M.;
1666
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667

Organometallics
ARTICLE
(k) Ruiz, J.; Berros, A.; Perandones, B. F.; Vivanco, M. Dalton Trans.
2009, 6999. (l) Huertos, M. A.; Pꢀerez, J.; Riera, L.; Díaz, J.; Lꢀopez, R.
Chem.—Eur. J. 2010, 16, 8495. (m) Dobereiner, G. E.; Chamberlin, C. A.;
Schley, N. D.; Crabtree, R. H. Organometallics 2010, 29, 5728.
(n) Miranda-Soto, V.; Grotjahn, D. B.; Cooksy, A. L.; Golen, J. A.; Moore,
C. E.; Rheingold, A. L. Angew. Chem., Int. Ed. 2011, 50, 631.
(24) H€aller, L. J. L.; Macgregor, S. A. Eur. J. Inorg. Chem.
2009, 2000.
(25) Song, G.; Su, Y.; Periana, R. A.; Crabtree, R. H.; Han, K.; Zhang,
H.; Li, X. Angew. Chem., Int. Ed. 2010, 49, 912.
(26) McGibbon, G. A.; Heinemann, C.; Lavorato, D. J.; Schwarz, H.
Angew. Chem. Ind. Ed. Engl. 1997, 36, 1478.
(32) (a) Buil, M. L.; Esteruelas, M. A.; O~nate, E.; Ruiz, N. Organo-
metallics 1998, 17, 3346. (b) Esteruelas, M. A.; Gutiꢀerrez-Puebla, E.;
Lꢀopez, A. M.; On~ate, E.; Tolosa, J. I. Organometallics 2000, 19, 275.
(33) (a) Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics
2005, 24, 4343. (b) Castarlenas, R.; Esteruelas, M. A.; O~nate, E.
Organometallics 2007, 26, 2129. (c) Castarlenas, R.; Esteruelas, M. A.;
O~nate, E. Organometallics 2007, 26, 3082. (d) Castarlenas, R.; Esteruelas,
M. A.; Lalrempuia, R.; Olivꢀan, M.; On~ate, E. Organometallics 2008, 27, 795.
(e) Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2008,
27, 3240. (f) Buil, M. L.; Castarlenas, R.; Esteruelas, M. A.; Izquierdo, S.;
Lalrempuia, R.; On~ate, E. Organometallics 2010, 29, 876.
(34) Chaloner, P. A.; Esteruelas, M. A.; Joꢀo, F.; Oro, L. A. Homo-
geneous Hydrogenation; Kluwer: Dordrecht, The Netherlands, 1994;
Chapter 3.
(27) Sini, G.; Eisenstein, O.; Crabtree, R. H. Inorg, Chem. 2002,
41, 602.
(35) Esteruelas, M. A.; Fernꢀandez, I.; Fuertes, S.; Lꢀopez, A. M.;
O~nate, E.; Sierra, M. A. Organometallics 2009, 28, 4876.
(36) Sabo-Etienne, S.; Chaudret, B. Chem. Rev. 1998, 98, 2077.
(37) Gardiner, M. G.; Herrmann, W. A.; Reisinger, C.-P.; Schwarz,
J.; Spiegler, M. J. Organomet. Chem. 1999, 572, 239.
(38) Aracama, M.; Esteruelas, M. A.; Lahoz, F. J.; Lꢀopez, J. A.; Meyer,
U.; Oro, L. A.; Werner, H. Inorg. Chem. 1991, 30, 288.
(39) Siegel, J. S.; Anet, F. A. L. J. Org. Chem. 1988, 53, 2629.
(40) SADABS: Area-Detector Absorption Correction; Bruker-AXS,
Madison, WI, 1996.
(28) (a) Esteruelas, M. A.; Fernꢀandez-Alvarez, F. J.; O~nate, E. J. Am.
Chem. Soc. 2006, 128, 13044. (b) Alvarez, E.; Conejero, S.; Paneque, M.;
ꢀ
Petronilho, A.; Poveda, M. L.; Serrano, O.; Carmona, E. J. Am. Chem. Soc.
2006, 128, 13060. (c) Wiedemann, S. H.; Lewis, J. C.; Ellman, J. A.;
Bergman, R. G. J. Am. Chem. Soc. 2006, 128, 2452. (d) Buil, M. L.;
Esteruelas, M. A.; Garcꢀes, K.; Olivꢀan, M.; O~nate, E. J. Am. Chem. Soc.
2007, 129, 10998. (e) Esteruelas, M. A.; Fernꢀandez-Alvarez, F. J.; O~nate,
ꢀ
E. Organometallics 2007, 26, 5239. (f) Alvarez, E.; Conejero, S.; Lara, P.;
Lꢀopez, J. A.; Paneque, M.; Petronilho, A.; Poveda, M. L.; del Rio, D.;
Serrano, O.; Carmona, E. J. Am. Chem. Soc. 2007, 129, 14130. (g) Lewis,
J. C.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2007, 129, 5332. (h)
Begum, R.; Komuro, T.; Tobita, H. Chem. Lett. 2007, 36, 650. (i) Buil.,
M. L.; Esteruelas, M. A.; Garcꢀes, K.; Olivꢀan, M.; On~ate, E. Organome-
tallics 2008, 27, 4680. (j) Esteruelas, M. A.; Fernꢀandez-Alvarez, F. J.;
O~nate, E. Organometallics 2008, 27, 6236. (k) Berman, A. M.; Lewis,
J. C.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2008, 130, 14926.
(l) Lewis, J. C.; Berman, A. M.; Bergman, R. G.; Ellman, J. A. J. Am. Chem.
Soc. 2008, 130, 2493. (m) Gribble, M. W., Jr.; Ellman, J. A.; Bergman,
R. G. Organometallics 2008, 27, 2152. (n) Song, G.; Li, Y.; Chen, S.; Li, X.
Chem. Commun. 2008, 3558. (o) Song, G.; Zhang, Y.; Su, Y.; Deng, W.;
Han, K.; Li, X. Organometallics 2008, 27, 6193. (p) Conejero, S.; Lara, P.;
Paneque, M.; Petronilho, A.; Poveda, M. L.; Serrano, O.; Vattier, F.;
(41) (a) SHELXTL Package v. 6.10; Bruker-AXS, Madison, WI,
2000. (b) Sheldrick, G. Acta Crystallogr. 2008, A64, 112.
(42) Frisch, M. J.; et al. Gaussian 03, Revision C.02; Gaussian, Inc.,
Wallingford, CT, 2004.
ꢀ
Alvarez, E.; Maya, C.; Salazar, V.; Carmona, E. Angew. Chem., Int. Ed.
2008, 47, 4380. (q) Esteruelas, M. A.; Fernꢀandez-Alvarez, F. J.; Olivꢀan,
M.; O~nate, E. Organometallics 2009, 28, 2276. (r) Paneque, M.; Poveda,
ꢀ
M. L.; Vattier, F.; Alvarez, E.; Carmona, E. Chem. Commun. 2009, 5561.
ꢀ
(s) Alvarez, E.; Hernꢀandez, Y. A.; Lꢀopez-Serrano, J.; Maya, C.; Paneque,
M.; Petronilho, A.; Poveda, M. L.; Salazar, V.; Vattier, F.; Carmona, E.
Angew. Chem., Int. Ed. 2010, 49, 3496.
(29) (a) Barea, G.;Esteruelas, M. A.;Lledꢀos, A.;Lꢀopez, A. M.;O~nate, E.;
Tolosa, J. I. Organometallics 1998, 17, 4065. (b) Barrio, P.; Castarlenas, R.;
Esteruelas, M. A.; Lledꢀos, A.; Maseras, F.; O~nate, E.; Tomꢀas, J. Organome-
tallics 2001, 20, 442. (c) Barrio, P.; Castarlenas, R.; Esteruelas, M. A.; O~nate,
E. Organometallics 2001, 20, 2635. (d) Barrio, P.; Esteruelas, M. A.; O~nate, E.
Organometallics 2004, 23, 1340. (e) Barrio, P.; Esteruelas, M. A.; O~nate, E
Organometallics 2004, 23, 3627. (f) Baya, M.; Eguillor, B.; Esteruelas, M. A.;
Lledꢀos, A.; Olivꢀan, M.; O~nate, E. Organometallics 2007, 26, 5140. (g)
Esteruelas, M. A.;Masamunt, A. B.;Olivꢀan, M.;O~nate, E.; Valencia, M. J. Am.
Chem. Soc. 2008, 130, 11612. (h) Esteruelas, M. A.; Forcꢀen, E.; Olivꢀan, M.;
O~nate, E. Organometallics 2008, 27, 6188. (i) Eguillor, B.; Esteruelas, M. A.;
García-Raboso, J.; Olivꢀan, M.; O~nate, E. Organometallics 2009, 28, 3700. (j)
Esteruelas, M. A.; Fernꢀandez, I.; Herrera, A.; Martín-Ortiz, M.; Martinez-
Alvarez, R.; Olivꢀan, M.; O~nate, E.; Sierra, M. A.; Valencia, M. Organometallics
2010, 29, 976.
(30) (a) Atencio, R.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.;
Ruiz, N. Inorg. Chem. 1995, 34, 1004. (b) Esteruelas, M. A.; Lahoz, F. J.;
Lꢀopez, A. M.; O~nate, E.; Oro, L. A.; Ruiz, N.; Sola, E.; Tolosa, J. I. Inorg.
Chem. 1996, 35, 7811. (c) Castillo, A.; Barea, G.; Esteruelas, M. A.;
Lahoz, F. J.; Lledꢀos, A.; Maseras, F.; Modrego, J.; O~nate, E.; Oro, L. A.;
Ruiz, N.; Sola, E. Inorg. Chem. 1999, 38, 1814. (d) Buil, M. L.; Esteruelas,
M. A.; Garcꢀes, K.; García-Raboso, J.; Olivꢀan, M. Organometallics 2009,
28, 4606.
(31) Eguillor, B.; Esteruelas, M. A.; Olivꢀan, M.; Puerta, M. Organo-
metallics 2008, 27, 445.
1667
dx.doi.org/10.1021/om101173e |Organometallics 2011, 30, 1658–1667