A Capped Octahedral MHC6Compound of a Platinum Group Metal

Article abstract of DOI:10.1002/chem.201601729

A MHC₆complex of a platinum group metal with a capped octahedral arrangement of donor atoms around the metal center has been characterized. This osmium compound OsH{κ²-C,C-(PhBIm-C₆H₄)}₃, which reacts with HBF₄to afford the 14 e^?species [Os{κ²-C,C-(PhBIm-C₆H₄)}(Ph₂BIm)₂]BF₄stabilized by two agostic interactions, has been obtained by reaction of OsH₆(PiPr₃)₂with N,N′-diphenylbenzimidazolium chloride ([Ph₂BImH]Cl) in the presence of NEt₃. Its formation takes place through the C,C,C-pincer compound OsH₂{κ³-C,C,C-(C₆H₄-BIm-C₆H₄)}(PiPr₃)₂, the dihydrogen derivative OsCl{κ²-C,C-(PhBIm-C₆H₄)}(η²-H₂)(PiPr₃)₂, and the five-coordinate osmium(II) species OsCl{κ²-C,C-(PhBIm-C₆H₄)}(PiPr₃)₂.

Full text of DOI:10.1002/chem.201601729

DOI: 10.1002/chem.201601729
Communication
&
Agostic Interactions
A Capped Octahedral MHC6 Compound of a Platinum Group
Metal
Beatriz Eguillor,[a] Miguel A. Esteruelas,*[a] Virginia Lezµun,[a] Montserrat Olivµn,[a]
Enrique OÇate,[a] Jui-Yi Tsai,[b] and Chuanjun Xia[b]
Seven-coordinate “blue-blood” organometallic compounds
Abstract: A MHC6 complex of a platinum group metal
with a capped octahedral arrangement of donor atoms
are known for 5 and 6 group metals, have a MC7 core, and
have been stabilized by using linear isocyanide ligands. Ellis
around the metal center has been characterized. This
and co-workers have reported homoleptic heptakis(isocya-
osmium compound OsH{k2-C,C-(PhBIm-C6H4)}3, which
reacts with HBF4 to afford the 14eÀ species [Os{k2-C,C-
nide)-vanadium(I), -niobium(I), and -tantalum(I) derivatives. Al-
though for the coordination number seven the most common
(PhBIm-C6H4)}(Ph2BIm)2]BF4 stabilized by two agostic inter-
polyhedron is the pentagonal bipyramid,[5] the VC7 core has
actions, has been obtained by reaction of OsH6(PiPr3)2
the form of a distorted monocapped trigonal prism.[6] However,
with N,N’-diphenylbenzimidazolium chloride ([Ph2BImH]Cl)
the TaC7 core is best described as a capped octahedron slightly
in the presence of NEt3. Its formation takes place through
distorted towards a capped trigonal prism.[7] The heptakis(iso-
the C,C,C-pincer compound OsH2{k3-C,C,C-(C6H4-BIm-
cyanide)-chromium(II), -molybdenum(II), and -tungsten(II)
C6H4)}(PiPr3)2, the dihydrogen derivative OsCl{k2-C,C-
counterparts have been described by the groups of Lippard,[8]
(PhBIm-C6H4)}(h2-H2)(PiPr3)2, and the five-coordinate osmi-
Walton,[9] and San Filippo.[10] For these compounds, a capped
um(II) species OsCl{k2-C,C-(PhBIm-C6H4)}(PiPr3)2.
octahedral arrangement or a capped trigonal prism of C2v sym-
metry have been also observed, depending upon the metal
center and the substituent of the isocyanide.
Transition-metal complexes containing only carbon and hydro-
gen donor atoms at the metal coordination sphere form the
family of “blue-blood” organometallic compounds, which have
played a determinant role in the conceptual development of
the current chemistry. They are stabilized by a metal center in
low oxidation state and have usually four-, five-, or six-coordi-
nation numbers.[1]
We here report the first seven-coordinate “blue-blood” or-
ganometallic compound of a platinum group metal. In contrast
to those of group 5 and 6 metals, it has a MHC6 core and is
stabilized by three orthometalated N-heterocyclic carbene
(NHC) ligands.
Saturated transition-metal polyhydride complexes have the
ability of losing molecular hydrogen to afford unsaturated spe-
cies, which coordinate and subsequently activate s-bonds. In
agreement with this, the hexahydride complex OsH6(PiPr3)2 (1)
has proven to promote the chelate-assisted CÀH cleavage in
a wide range of organic molecules,[11] as well as the direct acti-
vation of the CÀH bond situated between the nitrogen atoms
of imidazolium and benzimidazolium salts.[12] In accordance
with this ability, complex 1 is able to induce the orthometala-
tion of a phenyl substituent of N,N’-diphenylbenzimidazolium
chloride ([Ph2BImH]Cl) in addition to the coordination of the
benzimidazolylidene moiety. As a consequence of this, the
treatment of its decalin solutions with 3.0 equiv of the salt and
3.0 equiv of NEt3, under reflux, for 20 h leads to the seven-co-
ordinate MHC6 compound OsH{k2-C,C-(PhBIm-C6H4)}3 (2 in
Scheme 1), which was isolated as a white solid in 63% yield.
Figure 1 shows a view of the structure of 2. The coordina-
tion polyhedron around the osmium atom can be described as
a capped octahedron of C3 symmetry with the OsÀH bond
contained in the C3 symmetry axis and the hydride ligand lo-
cated at the center of the trigonal face defined by the carbene
carbon atoms. The analysis of the orbitals of the molecule re-
veals that this hydride position allows the interaction between
the s orbital of the hydride and the formally vacant p orbitals
of the carbene carbon atoms (Figure 2). The presence of the
The oxidation state of the metal center determines the coor-
dination number and the geometry of the complexes. High ox-
idation states are mainly stabilized with oxidizing ligands such
as oxygen and halides, in particular fluoride and chloride. Hy-
dride, with a minimal steric influence, is also ideal to achieve
high coordination numbers.[2] With the notable exception of
the methyl group[3] and combinations cyclopentadienyl-hy-
dride,[4] donor carbon ligands have rarely stabilized “blue-
blood” organometallic compounds in high oxidation states
and coordination numbers higher than six.
[a] Dr. B. Eguillor, Prof. Dr. M. A. Esteruelas, V. Lezµun, Dr. M. Olivµn,
Dr. E. OÇate
Departamento de Química Inorgµnica
Instituto de Síntesis Química y Catµlisis HomogØnea (ISQCH)
Centro de Innovación en Química Avanzada (ORFEO-CINQA)
Universidad de Zaragoza - CSIC, 50009 Zaragoza (Spain)
E-mail: maester@unizar.es
[b] Dr. J.-Y. Tsai, Dr. C. Xia
Universal Display Corporation
375 Phillips Boulevard, Ewing, New Jersey 08618 (USA)
Supporting information for this article, which includes experimental details
and CCDC information, is available on the WWW under
http://dx.doi.org/10.1002/chem.201601729.
Chem. Eur. J. 2016, 22, 9106 – 9110
9106
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
the reductive elimination of the hydride and other orthometa-
lated phenyl. The salt was isolated as an orange solid in 85%
yield and characterized by X-ray diffraction analysis. The struc-
ture (Figure 3) reveals an octahedral arrangement of ligands
around the metal center, including agostic interactions be-
tween the osmium atom and the formed bonds, which are
trans disposed to the remaining orthometalated chelate group.
Scheme 1. Preparation and protonation of complex 2.
Figure 3. ORTEP diagram of the cation of complex 3 (50% probability ellip-
soids). Hydrogen atoms (except those involved in the agostic interactions)
are omitted for clarity. Selected bond lengths and angles are given in
Table S2 in the Supporting Information.
Figure 1. ORTEP diagram of complex 2 (50% probability ellipsoids). Hydro-
gen atoms (except the hydride) are omitted for clarity. Selected bond
lengths and angles are given in Table S1 in the Supporting Information.
The agostic interactions are strongly supported by the OsÀ
C(22) (2.473(6) Š), OsÀH(22) (1.92(6) Š) and C(22)ÀH(22)
(1.12(6) Š) distances and the OsÀC(41) (2.452(6) Š), OsÀH(41)
(1.83(6) Š) and C(41)ÀH(41) (1.13(6) Š) bond lengths, which
compare well with those reported for other Os-H-C agostic in-
teractions.[13] Furthermore, the respective rbp values of 0.7(1)
and 0.6(1) Š agree well with those calculated for other d agos-
tic interactions.[14] In accordance with these values, the agostic
interactions persist in [D2]dichloromethane at temperatures
1
lower than 223 K. Thus, the H NMR spectra at these tempera-
tures contain two phenyl resonances at 1.86 and 1.49 ppm,
whereas the INEPT 13C spectrum at 213 K shows CÀH coupling
constants of 114 and 112 Hz for phenyl resonances at 98.4 and
92.9 ppm, respectively, which are about 50 Hz lower than the
Figure 2. HOMO-5 and HOMO-32 of complex 2 calculated at the B3LYP/(6-
31 g**+ SDD) level (isosurface value 0.02).
1
other JCÀH coupling constants. This extreme case[15] of two
agostic interactions is forced by the exceptionally high Lewis
acidity of the generated 14-valence-electron, non p-stabilized,
osmium(II) cation.
hydride in the complex is consistent with
a signal at
À9.90 ppm in the 1H NMR spectrum.
Chloride plays a fundamental role in the formation of 2, in
agreement with previous observations indicating that the
anion markedly influences the stoichiometry of the resulting
complex and the coordination fashion of the NHC ligand in re-
actions of imidazolium and benzimidazolium salts with polyhy-
Complex 2 has Brønsted base character. Thus, in dichlorome-
thane, it reacts with HBF4·OEt2 to afford the salt [Os{k2-C,C-
(PhBIm-C6H4)}(Ph2BIm)2]BF4 (3 in Scheme 1), as a result of the
protonation of one of the orthometalated phenyl groups and
Chem. Eur. J. 2016, 22, 9106 – 9110
www.chemeurj.org
9107
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
drides of platinum group metals.[16] When [Ph2BImH]BF4 was
used instead of the chloride salt, the dihydride-osmium(IV)
complex OsH2{k3-C,C,C-(C6H4-BIm-C6H4)}(PiPr3)2 (4 in Scheme 2)
was formed,[17] as a result of the ortho-CH bond activation of
both phenyl substituents. This compound is also notable,
Figure 4. ORTEP diagram of complex 4 (50% probability ellipsoids). Hydro-
gen atoms (except the hydrides) are omitted for clarity. Selected bond
lengths and angles are given in Table S3 in the Supporting Information.
Scheme 2. Synthesis of complexes 4, 5 and 6, and formation of complex 2
from complexes 4 and 6.
[Ph2BImH]Cl and 2.0 equiv of NEt3 in toluene, under reflux.
Under these conditions, a mixture of the chloride-osmium(II)-
dihydrogen derivative OsCl{k2-C,C-(PhBIm-C6H4)}(h2-H2)(PiPr3)2
(5) and the five-coordinate species, resulting from the dihydro-
gen dissociation, OsCl{k2-C,C-(PhBIm-C6H4)}(PiPr3)2 (6) was ob-
tained. Because the difference in stoichiometry between 4 and
5 is a HCl molecule, we added HCl dissolved in toluene to a tol-
uene solution of 4 and, as expected, complex 5 was formed,
which loses H2 to afford 6. Both 5 and 6 are intermediates in
the formation of 2. Treatment of the mixture, in decalin, with
2.0 equiv of [Ph2BImH]BF4 and 2.0 equiv of NEt3, under reflux,
also yields 2 (Scheme 2). These reactions suggest that the role
of the chloride anion is to stabilize the five-coordinate osmi-
um(II) intermediate 6: the p-donor ability of the chloride anion
partially cancels the unsaturated character of the metal center.
Complexes 5 and 6 co-crystallized in a solution of toluene
layered with methanol to afford crystals suitable for X-ray dif-
fraction analysis. Figure 5 and Figure 6 show the structures of
both compounds. The geometry around the osmium atom of
5 can be rationalized as a distorted octahedron with trans-
phosphines. In the perpendicular plane the chloride ligand is
disposed trans to the carbene carbon atom, as expected for
the p-acceptor character of the benzimidazolylidene unit.[12c]
The geometry around the osmium atom of 6 can be described
as a distorted trigonal bipyramid with apical phosphines and
mainly for two reasons: 1) it is the first species containing a dia-
nionic C,C,C-pincer ligand in the osmium chemistry[18] and
2) the orthometalation of both phenyl substituents has no
precedent for N,N’-diphenylbenzimidazolium and only once
has been reported for N,N’-(diaryl)imidazolium counterparts.[19]
Furthermore, it demonstrates the versatility of the NHC ligand,
which can stabilize highly unsaturated species by means of
agostic interactions and can act as neutral monodentate,[20]
monoanionic chelate,[21] and dianionic pincer through reversi-
ble CÀH bond activations of the phenyl groups.
Complex 4, which was isolated as colorless crystals in 49%
yield, was also characterized by X-ray diffraction analysis. The
structure (Figure 4) proves the formation of the pincer ligand
with the activated phenyl groups situated pseudo trans (C(9)-
Os-C(15)=144.92(15)8). In contrast to 2, the coordination ge-
ometry around the metal center can be rationalized as a dis-
torted pentagonal bipyramid with axial phosphines and the
hydrides, separated by 1.63(4) Š, lying in the equatorial plane
1
along with the pincer. At room temperature, the H, 13C{1H},
and 31P{1H} NMR spectra, in [D6]benzene, are consistent with its
X-ray structure, showing equivalent hydrides, metalated phenyl
1
groups, and phosphines. Thus, the H NMR spectrum contains
only one triplet (JHÀP =19.0 Hz) at À5.96 ppm for the hydride li-
gands, the 13C{1H} NMR spectrum shows only one triplet (JCÀP
=
6.3 Hz) at 149.8 ppm for the metalated carbon atom of the ac-
tivated phenyl groups, and the 31P{1H} NMR spectrum contains
a singlet at 10.5 ppm for the phosphines.
inequivalent angles of 76.5(3)8 (C-Os-C), 120.62(18)8 (Cl-Os-Caryl)
and 162.87(19)8 (Cl-Os-CBIm) within the Y-shaped equatorial
plane.
Complex 4 is an intermediate in the formation of 2. In ac-
cordance with this, treatment of decalin solutions of 4 with
2.0 equiv of [Ph2BImH]Cl and 2.0 equiv of NEt3, under reflux,
also led to 2. The question is: what is the role of the chloride
anion? In the search for information in this direction and some
new intermediate, we treated complex 1 with 1.0 equiv of
The presence of the dihydrogen ligand in 5 is strongly sup-
ported by its H NMR spectrum in [D2]dichloromethane, which
1
contains the characteristic dihydrogen resonance at
À4.27 ppm with a 400 MHz T1(min) value of 15Æ1 ms at 213 K.
This value corresponds to a HÀH distance of 0.84 Š (fast spin-
ning) or 1.06 Š (slow spinning).[22] In accordance with the latter,
Chem. Eur. J. 2016, 22, 9106 – 9110
www.chemeurj.org
9108
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
pot synthesis procedure by reaction of the hexahydride
OsH6(PiPr3)2 with N,N’-diphenylbenzimidazolium chloride. The
anion of the salt plays a main role during the process, stabiliz-
ing a key intermediate osmium(II) intermediate, and the NHC
ligand acts as both dianionic C,C,C-pincer and monoanionic
C,C-chelate.
Acknowledgements
Financial support from the MINECO of Spain (Projects
CTQ2014-52799-P and CTQ2014-51912-REDC), Gobierno de
Aragón (E35), FEDER, and the European Social Fund is acknowl-
edged.
Keywords: agostic interactions
·
capped octahedron
·
hydride · N-heterocyclic carbene · osmium
[1] Comprehensive Organometallic Chemistry III (Eds.-in-chief: R. H Crabtree,
D. M. Mingos), Elsevier, 2007.
[2] G. G. Hlatky, R. H. Crabtree, Coord. Chem. Rev. 1985, 65, 1–48.
[3] a) V. Pfennig, N. Robertson, K. Seppelt, Angew. Chem. Int. Ed. Engl. 1997,
36, 1350–1352; Angew. Chem. 1997, 109, 1410–1412; b) B. Roessler, K.
Seppelt, Angew. Chem. Int. Ed. Engl. 2000, 39, 1259–1261; Angew. Chem.
2000, 112, 1326–1329.
[4] a) W. A. Herrmann, H. G. Theiler, P. Kiprof, J. Tremmel, R. Blom, J. Organo-
met. Chem. 1990, 395, 69–84; b) C. A. Bayse, M. Couty, M. B. Hall, J. Am.
Chem. Soc. 1996, 118, 8916–8919; c) T. Shima, H. Suzuki, Organometal-
lics 2005, 24, 3939–3945; d) C. L. Gross, G. S. Girolami, Organometallics
2007, 26, 160–166.
Figure 5. ORTEP diagram of complex 5 (50% probability ellipsoids). Hydro-
gen atoms (except those of the dihydrogen molecule) are omitted for clarity.
Selected bond lengths and angles are given in Table S4 in the Supporting In-
formation.
[5] a) D. Casanova, P. Alemany, J. M. Bofill, S. Alvarez, Chem. Eur. J. 2003, 9,
1281–1295; b) F. VillafaÇe, Coord. Chem. Rev. 2014, 281, 86–99.
[6] M. E. Minyaev, J. E. Ellis, Acta Crystallogr. Sect. E 2015, 71, 431–434.
[7] M. V. Barybin, W. W. Brennessel, B. E. Kucera, M. E. Minyaev, V. L. Suss-
man, V. C. Young, Jr., J. E. Ellis, J. Am. Chem. Soc. 2007, 129, 1141–1150.
[8] a) D. L. Lewis, S. J. Lippard, J. Am. Chem. Soc. 1975, 97, 2697–2702;
b) D. J. Szalda, J. C. Dewan, S. J. Lippard, Inorg. Chem. 1981, 20, 3851–
3857; c) J. C. Dewan, S. J. Lippard, Inorg. Chem. 1982, 21, 1682–1684;
d) J. C. Dewan, W. S. Mialki, R. A. Walton, S. J. Lippard, J. Am. Chem. Soc.
1982, 104, 133–136.
[9] P. Brant, F. A. Cotton, J. C. Sekutowski, T. E. Wood, R. A. Walton, J. Am.
Chem. Soc. 1979, 101, 6588–6593.
[10] W. A. LaRue, A. T. Liu, J. San Filippo Jr., Inorg. Chem. 1980, 19, 315–320.
[11] a) M. A. Esteruelas, A. B. Masamunt, M. Olivµn, E. OÇate, M. Valencia, J.
Am. Chem. Soc. 2008, 130, 11612–11613; b) O. Crespo, B. Eguillor, M. A.
Esteruelas, I. Fernµndez, J. García-Raboso, M. Gómez-Gallego, M. Martín-
Ortiz, M. Olivµn, M. A. Sierra, Chem. Commun. 2012, 48, 5328–5330.
[12] a) B. Eguillor, M. A. Esteruelas, M. Olivµn, M. Puerta, Organometallics
2008, 27, 445–450; b) B. Eguillor, M. A. Esteruelas, J. García-Raboso, M.
Olivµn, E. OÇate, I. M. Pastor, I. PeÇafiel, M. Yus, Organometallics 2011,
30, 1658–1667; c) T. BolaÇo, M. A. Esteruelas, I. Fernµndez, E. OÇate, A.
Palacios, J.-Y. Tsai, C. Xia, Organometallics 2015, 34, 778–789; d) T.
BolaÇo, M. A. Esteruelas, M. P. Gay, E. OÇate, I. M. Pastor, M. Yus, Organo-
metallics 2015, 34, 3902–3908.
Figure 6. ORTEP diagrams of complex 6 (50% probability ellipsoids). Hydro-
gen atoms are omitted for clarity. Selected bond lengths and angles are
given in Table S5 in the Supporting Information.
[13] a) M. A. Esteruelas, F. J. Lahoz, E. OÇate, L. A. Oro, E. Sola, J. Am. Chem.
Soc. 1996, 118, 89–99; b) T. B. Wen, Z. Y. Zhou, C.-P. Lau, G. Jia, Organo-
metallics 2000, 19, 3466–3468; c) R. Castro-Rodrigo, M. A. Esteruelas,
A. M. López, E. OÇate, Organometallics 2008, 27, 3547–3555; d) B. Eguil-
lor, M. A. Esteruelas, I. Fernµndez, M. Gómez-Gallego, A. Lledós, M.
Martín-Ortiz, M. Olivµn, E. OÇate, M. A. Sierra, Organometallics 2015, 34,
1898–1910.
[14] R. H. Crabtree, E. M. Holt, M. Lavin, S. M. Morehouse, Inorg. Chem. 1985,
24, 1986–1992.
[15] Transition metal complexes with two agostic interactions are very rare.
For some relevant examples, see: a) D. Huang, J. C. Huffman, J. C. Bollin-
ger, O. Eisenstein, K. G. Caulton, J. Am. Chem. Soc. 1997, 119, 7398–
7399; b) A. C. Cooper, E. Clot, J. C. Huffman, W. E. Streib, F. Maseras, O.
a HÀD coupling constant of 20.2 Hz was obtained from the
species containing a partially deuterated h2-HD ligand.[23]
In conclusion, the first seven-coordinate “blue-blood” organ-
ometallic compound of a platinum group metal has been dis-
covered. This novel complex, which has a OsHC6 core with
three orthometalated NHC ligands and reacts with HBF4 to
afford a highly unsaturated 14-valence-electron fragment stabi-
lized by two agostic interactions, has been prepared in a one-
Chem. Eur. J. 2016, 22, 9106 – 9110
www.chemeurj.org
9109
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
Eisenstein, K. G. Caulton, J. Am. Chem. Soc. 1999, 121, 97–106; c) W. Bar-
atta, E. Herdtweck, P, Rigo, Angew. Chem. Int. Ed. 1999, 38, 1629–1631;
Angew. Chem. 1999, 111, 1733–1735; d) W. Baratta, C. Mealli, E. Herdt-
weck, A. Ienco, S. A. Mason, P. Rigo, J. Am. Chem. Soc. 2004, 126, 5549–
5562; e) N. M. Scott, V. Pons, E. D. Stevens, D. M. Heinekey, S. P. Nolan,
Angew. Chem. Int. Ed. 2005, 44, 2512–2515; Angew. Chem. 2005, 117,
2568–2571; f) T. M. Douglas, A. B. Chaplin, A. S. Weller, Organometallics
2008, 27, 2918–2921; g) L. J. Sewell, A. B. Chaplin, J. A. B. Abdalla, A. S.
Weller, Dalton Trans. 2010, 39, 7437–7439.
Chem. 2015, 54, 10998–11006 (N,C,C); d) Z.-Y. Li, W.-Y. Yu, C.-M. Che, C.-
K. Poon, R.-J. Wang, T. C. W. Mak, J. Chem. Soc. Dalton Trans. 1992,
1657–1661; e) J. Xiang, W. L. Man, S.-M. Yiu, S.-M. Peng, T.-C. Lau, Chem.
Eur. J. 2011, 17, 13044–13051 (O,N,O).
[19] N. Stylianides, A. A. Danopoulos, D. Pugh, F. Hancock, A. Zanotti-Gerosa,
Organometallics 2007, 26, 5627–5635.
[20] For previously reported complexes containing this ligand as neutral
monodentate, see: J. M. Berlin, K. Campbell, T. Ritter, T. W. Funk, A. Chle-
nov, R. H. Grubbs, Org. Lett. 2007, 9, 1339–1342.
[16] a) S. Gründemann, A. Kovacevic, M. Albrecht, J. W. Faller, R. H. Crabtree,
J. Am. Chem. Soc. 2002, 124, 10473–10481; b) L. N. Appelhans, D. Zuc-
caccia, A. Kovacevic, A. R. Chianese, J. R. Miecznikowski, A. Macchioni, E.
Clot, O. Eisenstein, R. H. Crabtree, J. Am. Chem. Soc. 2005, 127, 16299–
16311; c) M. Baya, B. Eguillor, M. A. Esteruelas, M. Olivµn, E. OÇate, Orga-
nometallics 2007, 26, 6556–6563; d) R. G. Alabau, B. Eguillor, J. Esler,
M. A. Esteruelas, M. Olivµn, E. OÇate, J.-Y. Tsai, C. Xia, Organometallics
2014, 33, 5582–5596.
[21] For previously reported complexes containing this ligand as mono-
anionic chelate, see: a) A. Tronnier, A. Pçthig, S. Metz, G. Wagenblast, I.
Münster, T. Strassner, Inorg. Chem. 2014, 53, 6346–6356; b) A. Tronnier,
U. Heinemeyer, S. Metz, G. Wagenblast, I. Muenster, T. Strassner, J.
Mater. Chem. C 2015, 3, 1680–1693.
[22] M. T. Bautista, E. P. Cappellani, S. D. Drouin, R. H. Morris, C. T. Schweitzer,
A. Sella, J. Zubkowski, J. Am. Chem. Soc. 1991, 113, 4876–4887.
[23] a) P. A. Maltby, M. Schlaf, M. Steinbeck, A. J. Lough, R. H. Morris, W. T.
Klooster, T. F. Koetzle, R. C. Srivastava, J. Am. Chem. Soc. 1996, 118,
5396–5407; b) T. A. Luther, D. M. Heinekey, Inorg. Chem. 1998, 37, 127–
132.
[17] Although the reaction takes place in the presence of NEt3, in this case,
Al2O3 is a more appropriate base.
[18] For dianionic-pincer ligands previously reported in the osmium chemis-
try, see: a) P. Gupta, R. J. Butcher, S. Bhattacharya, Inorg. Chem. 2003, 42,
5405–5411; b) R. Acharyya, S.-M. Peng, G.-H. Lee, S. Bhattacharya, Inorg.
Chem. 2003, 42, 7378–7380 (C,N,X (X=C, O)); c) L. Casarrubios, M. A.
Esteruelas, C. Larramona, J. G. Muntaner, E. OÇate, M. A. Sierra, Inorg.
Received: April 13, 2016
Published online on June 2, 2016
Chem. Eur. J. 2016, 22, 9106 – 9110
www.chemeurj.org
9110
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim