Multiple C-H bond activation of phenyl-substituted pyrimidines and triazines promoted by an osmium polyhydride: Formation of osmapolycycles with three, five, and eight fused rings

Article abstract of DOI:10.1021/om901030q

The reactions of the hexahydride complex OsH₆(P ⁱPr₃)₂ (1) with 4,5-dimethyl-2,6-bis(4- methylphenyl)pyrimidine (H₂Ll), 2,4,6-tris-(4-methylphenyl)-l,3,5- triazine (H₄L2), and 2,4,6-triphenylpyrimidine (H₄L3) have been studied. Complex 1 reacts with H₂Ll to give a mixture of the metallapolycyclic derivatives OsH₃(HLI)(PⁱPr ₃J₂ (2) and OsH₂(L1)(PⁱPr ₃)₂ (3). Compound 2 arises from the coordination of the N3-pyrimidine nitrogen atom to osmium and the ortho-CH bond activation of the C2-bonded phenyl group. The formation of 3 involves the coordination of the N1-pyrimidine nitrogen atom to osmium and the ortho-CH bond activation of both phenyl groups. The reaction of 1 with H₄L2 leads to a mixture of OsH₂(H₂L2)(PⁱPr₃)₂ (4) and (P'Pr₃)₂H₂Os(L2)OsH₂(PiPr ₃)₂ (5), containing five and eight fused rings, respectively. Complex 4 results from the coordination of the N1-triazine nitrogen atom to osmium and the ortho-CH bond activation of the phenyl groups at positions 2 and 6 of the triazine ring. Complex 5 results from the coordination of the N1 and N3 of triazine to two different metal centers along with a double ortho-CH bond activation in each proximal phenyl group. Complex 1 reacts with H₄L3 to afford OsH₂(H₂L3)(PⁱPr ₃)₂ (6) and (PⁱPr₃) ₂H₂Os(L3)OsH₂(PⁱPr₃) ₂ (7), which are related to 4 and 5, respectively. Complexes 2,3,4, and 5 have been characterized by X-ray diffraction analysis. The structures prove the planarity of their cores and suggest electron derealization through the polycyclic system. Quantum chemical calculations (DFT level) on model compounds clearly indicate that the Os-C and Os-N bonds of the newly formed metallapolycycles exhibit a remarkable double-bond character that is higher for the Os-C bond, in very good agreement with the experimental findings.

Full text of DOI:10.1021/om901030q

976 Organometallics 2010, 29, 976–986
DOI: 10.1021/om901030q
Multiple C-H Bond Activation of Phenyl-Substituted Pyrimidines and
Triazines Promoted by an Osmium Polyhydride: Formation of
Osmapolycycles with Three, Five, and Eight Fused Rings
,†
‡
‡
Miguel A. Esteruelas,* Israel Fernandez, Antonio Herrera, Mamen Martı
´
n-Ortiz,‡
ꢀ
nez-Alvarez, Montserrat Olivan, Enrique Onate, Miguel A. Sierra,* and
‡
†
†
,‡
ꢀ
ꢀ
~
Roberto Martı
´
Marta Valencia†
†
´
ꢀ
ꢀ
Departamento de Quımica Inorganica, Instituto de Ciencia de Materiales de Aragon, Universidad de
´
‡
Zaragoza, CSIC, 50009 Zaragoza, Spain and Departamento de Quımica Organica, Facultad de Quımica,
´
Universidad Complutense, 28040 Madrid, Spain
ꢀ
Received November 30, 2009
The reactions of the hexahydride complex OsH6(PiPr3)2 (1) with 4,5-dimethyl-2,6-bis(4-methyl-
phenyl)pyrimidine (H2L1), 2,4,6-tris-(4-methylphenyl)-1,3,5-triazine (H4L2), and 2,4,6-triphenyl-
pyrimidine (H4L3) have been studied. Complex 1 reacts with H2L1 to give a mixture of the
metallapolycyclic derivatives OsH3(HL1)(PiPr3)2 (2) and OsH2(L1)(PiPr3)2 (3). Compound 2 arises
from the coordination of the N3-pyrimidine nitrogen atom to osmium and the ortho-CH bond
activation of the C2-bonded phenyl group. The formation of 3 involves the coordination of the
N1-pyrimidine nitrogen atom to osmium and the ortho-CH bond activation of both phenyl groups.
The reaction of 1 with H4L2 leads to a mixture of OsH2(H2L2)(PiPr3)2 (4) and (PiPr3)2H2Os-
(L2)OsH2(PiPr3)2 (5), containing five and eight fused rings, respectively. Complex 4 results from the
coordination of the N1-triazine nitrogen atom to osmium and the ortho-CH bond activation of the
phenyl groups at positions 2 and 6 of the triazine ring. Complex 5 results from the coordination of the
N1 and N3 of triazine to two different metal centers along with a double ortho-CH bond activation in
each proximal phenyl group. Complex 1 reacts with H4L3 to afford OsH2(H2L3)(PiPr3)2 (6) and
(PiPr3)2H2Os(L3)OsH2(PiPr3)2 (7), which are related to 4 and 5, respectively. Complexes 2, 3, 4, and 5
have been characterized by X-ray diffraction analysis. The structures prove the planarity of their
cores and suggest electron delocalization through the polycyclic system. Quantum chemical calcula-
tions (DFT level) on model compounds clearly indicate that the Os-C and Os-N bonds of the newly
formed metallapolycycles exhibit a remarkable double-bond character that is higher for the Os-C
bond, in very good agreement with the experimental findings.
Introduction
Paneque and co-workers10 extended the aromatic metalla-
cycles to fused bicyclic compounds.11 Metallaisoindoles,12
metallabenzofurans,13 metallabenzothiabenzenes,14 metal-
laindolizines,15 metallabenzothiazoles, and metallabenzox-
azoles16 are new interesting classes of this type of compounds
with heteroatoms. The formation at -78 ꢀC of ruthenaphe-
nanthrene oxides has been reported,17 and the intermediacy
of rhenaphenanthrene species in the reactions of 2,20-di-
lithiobiphenyl with ReBr(CO)4(PPh3) has been suggested.18
Recently, 1,7-diosma-2,4-triaza-s-indacene and 1,7-diosma-
pyrrolo[3,4-f ]isoindole derivatives have also been prepared
and characterized by X-ray diffraction analysis.19 Never-
theless, lack of a flexible method to prepare fused polycyclic
metallacycles having more than three fused rings prevents
the study of the structural properties of these compounds.
The activation of C-H bonds is usually promoted by low-
valent complexes.20 The participation of high-valent com-
pounds, in particular hydride derivatives, in these reactions
is rare. In spite of this fact, previous work has shown that the
osmium(VI) complex OsH6(PiPr3)2 efficiently activates C-H
bonds of different organic substrates.9b,19,21 This reactivity
The synthesis of metallacycles has been a hot topic in
organometallic chemistry for nearly half a century.1 Reasons
behind this unabated and continuous interest in these classes
of compounds arise not only because of their involvement in
several C-C and C-X (X = heteroatom) forming reactions
but for their structural properties. This last aspect has
resulted in the preparation of metallabenzenes2 and related
metallacarbocycles.3 Substantial progress is being made
in the synthesis and the study of heteroatom-containing
species, including metallathiabenzenes,4 metallapyridines,5
metallapyryliums,6 metallathiophenes,7 metallapyrroles,8
and metallafurans.9
Higher π-electron metallacyclic compounds are also
known. The isolation of the first metallanaphthalene by
*Corresponding author. E-mail: maester@unizar.es (M.A.E.); sierraor@
quim.ucm.es (M.A.S.).
(1) (a) Bleeke, J. R. Chem. Rev. 2001, 101, 1205. (b) Wright, L. J.
Dalton Trans. 2006, 1821. (c) Landorf, C. W.; Haley, M. M. Angew. Chem.,
Int. Ed. 2006, 45, 3914. (d) Bleeke, J. R. Acc. Chem. Res. 2007, 40, 1035.
r
pubs.acs.org/Organometallics
Published on Web 01/15/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 4, 2010 977
makes OsH6(PiPr3)2 a good choice to build metallapolycycles
by reactions with appropriate phenyl-substituted pyrimidines
and triazines: 4,5-dimethyl-2,6-bis(4-methylphenyl)pyrimidine
(H2L1), 2,4,6-tris(4-methylphenyl)-1,3,5-triazine (H4L2), and
2,4,6-triphenylpyrimidine (H4L3). These reactions involve the
one-pot activation of one or two (for H2L1) and two or four
(for H4L2 and H4L3) C-H bonds to yield compounds of type
I, II, andIII, with three, five, and eight fused cycles, respectively
(Chart 1).
Chart 1
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Results and Discussion
Synthesis and Characterization of the New Osmapoly-
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978 Organometallics, Vol. 29, No. 4, 2010
Esteruelas et al.
Figure 1. Time versus composition of the reaction mixture of 1
with 4,5-dimethyl-2,6-bis(4-methylphenyl)pyrimidine. Com-
plexes 1 (b), 2 (9), and 3 (2). The progress of the reaction was
monitored by 31P{1H} NMR spectroscopy.
Figure 2. Molecular diagram of complex 2. Selected bond
lengths (A) and angles (deg): Os-C(8) 2.111(3), Os-N(1)
2.219(3), N(1)-C(4) 1.354(4), C(3)-C(4) 1.399(5), C(2)-C(3)
1.397(5), C(2)-N(2) 1.337(4), N(2)-C(1) 1.335(4), C(1)-N(1)
1.365(4), C(1)-C(7) 1.446(4), C(7)-C(8) 1.416(5), C(8)-C(9)
1.409(4), C(9)-C(10) 1.375(5), C(10)-C(12) 1.404(5), C(12)-
C(13) 1.371(5), C(13)-C(7) 1.401(5), H(01)-H(02) 1.46(4),
H(02)-H(03) 1.72(4); P(1)-Os-P(2) 165.72(3), C(8)-Os-
N(1) 77.08(11).
of 4,5-dimethyl-2,6-bis(4-methylphenyl)pyrimidine (H2L1)
produces after 32 h the quantitative transformation of the
starting compound into a mixture of the metallapolycyclic
derivatives OsH3(HL1)(PiPr3)2 (2) and OsH2(L1)(PiPr3)2 (3)
(Scheme 1).
These compounds result from the competition between a
single and double aromatic ortho-CH bond activation, direc-
ted by the pyrimidine nitrogen atoms. Compound 2 arises
from the thermal activation of 1 to give an OsH4(PiPr3)2
species, which coordinates the N3-pyrimidine nitrogen atom
and subsequently activates the ortho-C-H bond of the C2-
bonded phenyl group, with the concomitant loss of molecular
hydrogen. Formation of complex 3 follows an analogous
pattern, but now Os coordinates the N1-pyrimidine nitrogen
atom and the ortho-C-H bonds of both phenyl groups are
activated. Figure 1 shows that the formation of complex 3
(double CHbond activation) is slightly favored withrespect to
the formation of complex 2 (single CH bond activation).
Complexes 2 and 3 were isolated as pure red and orange
crystals in 25% and 36% yield, respectively, and charac-
1
terized by elemental analysis, IR, H, 31P{1H}, and 13C-
{1H} NMR spectroscopy, and X-ray diffraction analysis.
Figures 2 and 3 show views of the molecular geometry of 2
and 3, respectively.
Figure 3. Molecular diagram of complex 3. Selected bond
lengths (A) and angles (deg): Os-N(1) 2.101(4), Os-C(1)
2.106(5), Os-C(15) 2.110(5), N(1)-C(13) 1.353(7), N(1)-C(8)
1.361(7), C(1)-C(2) 1.410(7), C(1)-C(7) 1.422(7), C(2)-C(3)
1.381(7), C(3)-C(5) 1.387(8), C(5)-C(6) 1.373(8), C(6)-C(7)
1.399(7), C(7)-C(8) 1.458(8), C(8)-C(9A) 1.454(12), C(9A)-
C(11A) 1.370(13), N(2A)-C(13) 1.291(10), N(2A)-C(11A)
1.332(11), C(13)-C(14) 1.452(8), C(14)-C(20) 1.397(8), C(14)-
C(15) 1.415(7), C(15)-C(16) 1.414(7), C(16)-C(17) 1.392(7),
C(17)-C(19) 1.385(8), C(19)-C(20) 1.377(8); P(1)-Os-P(2)
161.95(5), N(1)-Os-C(1) 75.43(19), N(1)-Os-C(15) 75.51(19),
C(1)-Os-C(15) 150.9(2).
Complex 2 is a 6-osmapyrimido[2,1-a]isoindole derivative.
The metallatricycle core is planar (maximum deviation
0.117(3) A for N(2)), and the bond lengths lie between that
expected for single and double bonds. The Os-C(8) distance
2.111(3) A is similar to the Os-C bond lengths reported
for osmafurans,9b,c,e,f,h-k osmapyrroles,8e,f and related com-
pounds,12,19 while the Os-N(1) distance of 2.219(3) A com-
pares well with the Os-N bond lengths found in lower
π-electron osmacyclic nitrogen-containing compounds.8e,12
(13) Clark, G. R.; Johns, P. M.; Roper, W. R.; Wright, L. J.
Organometallics 2006, 25, 1771.
(14) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Moneti, S.;
The N-C bond lengths are between 1.335(4) and 1.365(4) A,
whereas the C-C distances lie between 1.375(5) and 1.446(4) A.
The coordination geometry around the osmium atom
of 2 can be described as a distorted pentagonal bipyramid
with axial phosphines (P(1)-Os-P(2) = 165.72(3)ꢀ) and the
hydride ligands lying in the equatorial plane. In agreement
with this phosphine disposition, the 31P{1H} NMR spectrum
in toluene-d8 contains a singlet at 21.4 ppm, which is tempera-
ture-invariant between 363 and 203 K. In contrast to the
31P{1H} NMR spectrum, the 1H NMR spectrum is tempera-
ture-dependent. At temperatures higher than 363 K, it shows a
single hydride resonance at -10.1 ppm, which is consistent
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Herrera, V.; Sanchez-Delgado, R. A. J. Am. Chem. Soc. 1994, 116, 4370.
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Article
Organometallics, Vol. 29, No. 4, 2010 979
with the operation of two thermally activated site exchange
processes, in agreement with the behavior of analogous
osmium trihydride derivatives. It has been proposed that these
exchanges go through dihydrogen states.22 Two decoalescences
are observed, the first one around 343 K, and the second
around 208 K. Thus, at 203 K, three resonances at -7.51,
-9.77, and -12.51 ppm are observed. A monodimensional
NOESY experiment at 223 K indicated that the latter corres-
ponds to the hydride ligand disposed cisoid to the metalated
phenyl group (H(03) in Figure 2). The 400 MHz T1(min) values
were found at 273 K, when the H(01) and H(02) hydride ligands
display only one resonance at -8.62 ppm. They (102 ( 3 ms for
H(01) and H(02) and 129 ( 3 ms for H(03)) are consistent with
the H(01)-H(02) and H(02)-H(03) separations of 1.46(4)
and 1.72(4) A, respectively, as determined by X-ray diffrac-
tion analysis. In agreement with a shorter H(01)-H(02)
separation, the activation enthalpy for the position exchange
between these hydrides is smaller than that for the position
exchange between H(02) and H(03), namely, 9 versus 11
bond length in 2, whereas the Os-C(1) (2.106(5) A) and
Os-C(15) (2.110(5) A) distances are statistically identical
with the Os-C bond lengths in the latter. Within each cycle,
the C-C distances are statistically identical with values
depending upon the cycle type: between 1.373(8) and
1.422(7) A for the six-membered C6 rings, between 1.415(7)
and 1.458(8) A for the five-membered rings, and between
1.370(13) and 1.454(12) A for the six-membered C4N2 ring.
The N(1)-C(13) (1.353(7) A), N(1)-C(8) (1.361(7) A), and
N(2A)-C(11A) (1.332(11) A) bond lengths are statistically
identical and slightly longer than the N(2A)-C(13)
(1.291(10) A) distance.
The coordination geometry around the osmium atom can
be rationalized as a distorted pentagonal bipyramid with the
phosphine ligands in axial positions (P(1)-Os-P(2) =
161.95(5) A) and the hydrides lying in the equatorial plane.
The H(01)-H(02) separation is 1.54(6) A. In agreement with
this ligand disposition, the 31P{1H} NMR spectrum in
benzene-d6 shows a singlet at 0.0 ppm, whereas the 1H
NMR spectrum contains two hydride resonances at -7.78
and -8.16 ppm, which appear as double triplets with H-P
and H-H coupling constants of 15.2 and 12.0 Hz, respec-
tively. In agreement with 2, in the 13C{1H} NMR spectrum,
the OsC resonances of the polycycle are observed at 183.4
and 173.9 ppm, as triplets with C-P coupling constants of
6.9 and 7.4 Hz, respectively.
kcal mol-1. The most noticeable resonance in the 13C{1H}
3
NMR spectrum in benzene-d6 at room temperature is a triplet
at 185.6 ppm having a C-P coupling constant of 7.3 Hz,
which corresponds to the metalated carbon atom C(8) of the
tricycle. This chemical shift compares well with those reported
for related polycyclic compounds containing metalated aro-
matic six-membered rings,9j,12,15b,19,21a,b,d while it is shifted
toward lower field with regard to the chemical shifts reported
for aryl derivatives (δ 125-160).12c,21c,23
Treatment of toluene solutions of 1 with 1.0 equiv of 2,4,6-
tris(4-methylphenyl)-1,3,5-triazine (H4L2) under reflux leads
after 36 h to the quantitative transformation of the hexa-
hydride starting compound into a 6:1 mixture of complexes
OsH2(H2L2)(PiPr3)2 (4) and (PiPr3)2H2Os(L2)OsH2(PiPr3)2
(5), according to Scheme 2. The increase of the 1:H4L2 molar
ratio produces an increase of the formed amount of 5.
However all attempts to obtain a single reaction product were
unsuccessful.
Complex 3 is a planar osmapolycycle (maximum deviation
0.211(5) A for C(5)) having five fused units (two five-
membered rings and three six-membered rings). The signifi-
cant electron delocalization through the polycyclic system
translates into bond lengths between those expected for
single and double bonds. Accordingly, the Os-N(1)
(2.101(4) A) distance is about 0.1 A shorter than the Os-N
(20) (a) Shilov, A. E.; Shteinman, A. A. Coord. Chem. Rev. 1977, 24,
97. (b) Crabtree, R. H. Chem. Rev. 1985, 85, 245. (c) Jones, W. D.; Feher, F. J.
Acc. Chem. Res. 1989, 22, 91. (d) Ryabov, A. D. Chem. Rev. 1990, 90, 403.
(e) Shilov, A. E.; Shul'pin, G. B. Chem. Rev. 1997, 97, 2879. (f) Crabtree,
R. H. J. Chem. Soc., Dalton Trans. 2001, 2437. (g) Labinger, J. A.; Bercaw,
J. E. Nature 2002, 417, 507. (h) Crabtree, R. H. J. Organomet. Chem. 2004,
689, 4083. (i) Carmona, E.; Paneque, M.; Santos, L. L.; Salazar, V. Coord.
Scheme 2
ꢀ
Chem. Rev. 2005, 249, 1729. (j) Esteruelas, M. A.; Lopez, A. M. Organo-
metallics 2005, 24, 3584. (k) Lersch, M.; Tilset, M. Chem. Rev. 2005, 105,
2471. (l) Jones, W. D. Inorg. Chem. 2005, 44, 4475. (m) Godula, K.; Sames,
D. Science 2006, 312, 67.
ꢀ
ꢀ
(21) (a) Barea, G.; Esteruelas, M. A.; Lledos, A.; Lopez, A. M.;
~
Onate, E.; Tolosa, J. I. Organometallics 1998, 17, 4065. (b) Barrio, P.;
ꢀ
~
ꢀ
Castarlenas, R.; Esteruelas, M. A.; Lledos, A.; Maseras, F.; Onate, E.; Tomas,
~
J. Organometallics 2001, 20, 442. (c) Barrio, P.; Esteruelas, M. A.; Onate, E.
~
Organometallics 2004, 23, 1340. (d) Barrio, P.; Esteruelas, M. A.; Onate, E.
Organometallics 2004, 23, 3627. (e) Baya, M.; Eguillor, B.; Esteruelas,
ꢀ
ꢀ
~
M. A.; Lledos, A.; Olivan, M.; Onate, E. Organometallics 2007, 26, 5140. (f)
ꢀ
~
Baya, M.; Eguillor, B.; Esteruelas, M. A.; Olivan, M.; Onate, E. Organome-
ꢀ
tallics 2007, 26, 6556. (g) Eguillor, B.; Esteruelas, M. A.; Olivan, M.; Puerta,
ꢀ
M. Organometallics 2008, 27, 445. (h) Esteruelas, M. A.; Forcen, E.; Olivan,
~
M.; Onate, E. Organometallics 2008, 27, 6188. (i) Eguillor, B.; Esteruelas,
ꢀ
~
M. A.; García-Raboso, J.; Olivan, M.; Onate, E. Organometallics 2009, 28,
3700.
ꢀ
(22) See for example: (a) Esteruelas, M. A.; Lahoz, F. J.; Lopez,
A. M.; Onate, E.; Oro, L. A.; Ruiz, N.; Sola, E.; Tolosa, J. I. Inorg.
~
Complex 4, which is related to 3, results from the coordi-
nation of the N1-triazine nitrogen atom to the metal center
followed by the activation of an ortho-CH bond of the phenyl
groups at the 2 and 6 positions of the triazine ring. Complex 5
is the result of the coordination of the N1 and N3 nitrogen
atoms of triazine to two osmium centers followed by a
double ortho-CH bond activation in each proximal phenyl
group, which results in the double C-H activation of the
~
Chem. 1996, 35, 7811. (b) Castillo, A.; Esteruelas, M. A.; Onate, E.; Ruiz, N.
J. Am. Chem. Soc. 1997, 119, 9691. (c) Castillo, A.; Barea, G.; Esteruelas,
M. A.; Lahoz, F. J.; Lledos, A.; Maseras, F.; Modrego, J.; Onate, E.; Oro,
L. A.; Ruiz, N.; Sola, E. Inorg. Chem. 1999, 38, 1814. (d) Castro-Rodrigo,
R.; Esteruelas, M. A.; Lopez, A. M.; Olivan, M.; Onate, E. Organometallics
2007, 26, 4498. (e) Baya, M.; Esteruelas, M. A.; Olivan, M.; Onate, E. Inorg.
Chem. 2009, 48, 2677.
(23) Liu, S. H.; Lo, S. T.; Wen, T. B.; Williams, I. D.; Zhou, Z. Y.;
Lau, C. P.; Jia, G. Inorg. Chim. Acta 2002, 334, 122. (b) Pool, D. H.;
Shapley, P. A. Organometallics 2004, 23, 2326.
ꢀ
~
ꢀ
ꢀ
~
ꢀ
~

980 Organometallics, Vol. 29, No. 4, 2010
Esteruelas et al.
Figure 4. Molecular diagram of complex 4. Selected bond
lengths (A) and angles (deg): Os-N(1) 2.085(3), Os-C(3)
2.118(3), Os-C(11) 2.128(3), N(1)-C(1) 1.354(4), N(1)-C(9)
1.356(4), N(2)-C(17) 1.342(4), N(2)-C(1) 1.346(4), N(3)-C(9)
1.338(4), N(3)-C(17) 1.339(4), C(1)-C(2) 1.447(4), C(2)-C(8)
1.398(5), C(2)-C(3) 1.418(4), C(3)-C(4) 1.423(4), C(4)-C(5)
1.392(5), C(5)-C(7) 1.406(5), C(7)-C(8) 1.371(5), C(9)-C(10)
1.439(4), C(10)-C(16) 1.396(4), C(10)-C(11) 1.425(4), C(11)-
C(12) 1.416(4), C(12)-C(13) 1.385(4), C(13)-C(15) 1.405(5),
C(15)-C(16) 1.367(5); P(1)-Os-P(2) 163.52(3), N(1)-Os-
C(3) 75.04(11), N(1)-Os-C(11) 75.44(11), C(3)-Os-C(11)
150.47(13).
Figure 5. Molecular diagram of complex 5. Selected bond
lengths (A) and angles (deg): Os(1)-N(1) 2.095(3), Os(2)-N(2)
2.089(4), Os(1)-C(11) 2.139(4), Os(2)-C(19) 2.161(4), Os(1)-
C(3) 2.184(4), Os(2)-C(8) 2.176(4), N(1)-C-(1) 1.329(5),
N(1)-C(9) 1.361(5), N(2)-C(1) 1.343(5), N(2)-C(17)
1.360(5), N(3)-C(17) 1.337(5), N(3)-C(9) 1.353(5), C(1)-C(2)
1.390(5), C(2)-C(8) 1.419(6), C(2)-C(3) 1.433(6), C(3)-C(4)
1.404(6), C(4)-C(5) 1.400(6), C(5)-C(7) 1.404(6), C(7)-C(8)
1.416(5), C(9)-C(10) 1.448(6), C(10)-C(16) 1.398(6), C(10)-
C(11) 1.437(5), C(11)-C(12) 1.398(6), C(12)-C(13) 1.396(6),
C(13)-C(15) 1.392(6), C(15)-C(16) 1.371(6), C(17)-C(18)
1.454(6), C(18)-C(24) 1.399(5), C(18)-C(19) 1.418(6), C(19)-
C(20) 1.406(6), C(20)-C(21) 1.390(5), C(21)-C(23) 1.392(6),
C(23)-C(24) 1.375(6); P(1)-Os(1)-P(2) 160.38(4), P(3)-
Os(2)-P(4) 157.43(4), N(1)-Os(1)-C(11) 73.57(14), N(1)-
Os(1)-C(3) 75.57(14), C(11)-Os(1)-C(3) 149.10(16), N(2)-
Os(2)-C(19) 72.65(14), N(2)-Os(2)-C(8) 75.53(14), C(19)-
Os(2)-C(8) 148.00(16).
phenyl group at the C2 position of the C3N3 ring by the two
Os centers. Overall, the reaction is a quadruple C-H activa-
tion by two Os centers in a single organic substrate.
Complex 4 was obtained as pure red crystals in 26% yield
and, as complexes 2 and 3, characterized by elemental
analysis, IR, 1H, 31P{1H}, and 13C{1H} NMR spectroscopy,
and X-ray diffraction analysis. Figure 4 shows a view of its
molecular geometry. Like in complex 3, the osmapolycycle
containing five fused units is planar (maximum deviation
0.263(4) A for C(17)). The Os-N(1) bond length of 2.085(3)
A as well as the Os-C(3) and Os-C(11) distances of 2.118(3)
and 2.128(3) A, respectively, are statistically identical with
the related parameters of 3. The C-N and C-C bond
lengths also agree well with those of complex 3. The C-N
distances lie in the range 1.338(4)-1.356(4) A, whereas the
C-C bond lengths are between 1.367(5) and 1.447(5) A.
The coordination geometry around the metal center can
also be rationalized as a distorted pentagonal bipyramid with
axial phosphines (P(1)-Os-P(2)) = 163.52(3)ꢀ) and the
hydrides lying in the equatorial plane. The 31P{1H} NMR
spectrum contains a singlet at 0.0 ppm, whereas the hydride
2.095(3) and 2.089(4) A, respectively, are statistically iden-
tical with the Os-N bond lengths in the other polycycles,
while the Os-C distances of 2.139(4) (Os(1)-C(11)),
2.161(4) (Os(2)-C(19)), 2.176(4) (Os(2)-C(8)), and 2.184(4)
(Os(2)-C(3)) A are between 0.04 and 0.08 A longer. The
N-C and C-C bond lengths also compare well with those of
2-4. The N-C distances lie in the range 1.329(5)-1.361(5) A,
whereas the C-C bond lengths are between 1.371(6) and
1.453(6) A.
The coordination geometries around the osmium atoms
are similar to those of the metal centers of 3 and 4, i.e.,
distorted pentagonal bipyramids with axial phosphines
(P(1)-Os(1)-P(2)) = 160.38(4)ꢀ and P(3)-Os(2)-P(4)) =
157.43(4)ꢀ) with the hydride ligands lying in the equatorial
plane. The 31P{1H}, 1H, and 13C{1H} NMR spectra are
consistent with this ligand distribution. Thus, the 31P{1H}
NMR spectrum contains a singlet at 2.5 ppm, whereas the
hydride ligands display at -7.13 and -8.71 ppm double
triplets with a H-H coupling constant of 8.0 Hz and H-P
coupling constants of 16.0 and 18.4 Hz, respectively. The
metalated carbon atoms of the polycycle give rise to two
triplets at 176.3 and 172.6 ppm in the 13C{1H} NMR
spectrum. The C-P coupling constants of 8.9 and 6.4 Hz,
respectively, are consistent with those observed in 3 and 4.
2,4,6-Triphenylpyrimidine (H4L3) has a higher tendency
to form the diosmapolycycle having eight fused units than
2,4,6-tris(4-methylphenyl)-1,3,5-triazine (H4L2). Treatment
under reflux of a toluene solution of 1 with 1.0 equiv of the
pyrimidine for 7 h affords a mixture of the osmapolycycle 6,
having five fused cycles, and the diosmapolycycle 7, having
1
ligands in the H NMR spectrum display at -7.30 ppm a
triplet with a H-P coupling constant of 15.6 Hz, which
agrees with this ligand disposition. In the 13C{1H} NMR
spectrum, the resonance corresponding to the equivalent
metalated carbon atoms appears at 179.4 ppm as a triplet
with a C-P coupling constant of 6.8 Hz.
A few red crystals of 5 suitable for an X-ray diffraction
study were obtained by slow diffusion of methanol into a
toluene solution of a 4:1 mixture of 4 and 5. Figure 5 shows a
view of its molecular geometry.
The structure proves the formation of a diosmapolycycle
having eight fused rings (four five-membered rings and four
six-membered rings), which is also almost planar (maximum
deviation 0.536(6) A for C(6)). The structural parameters
of this polycycle are similar to those observed in the poly-
cycles of 2-4. The Os(1)-N(1) and Os(2)-N(2) distances of

Article
Organometallics, Vol. 29, No. 4, 2010 981
eight fused cycles, in a 4:1 molar ratio. However, under the
same conditions, the treatment of 1 with 0.5 equiv of the
pyrimidine for 21 h quantitatively forms 7, which is isolated
as a dark red solid in 73% yield (Scheme 3).
the osmium atoms was investigated with the AIM (atoms in
molecules)25 and with the NBO (natural bond orbital)26
methods on the model compound 2M. Figure 6 shows the
2
contour line diagrams of the Laplacian distribution r F(r)
in the plane of the newly formed five-membered ring.
Both, the Os-N and Os-C bonds in 2M clearly exhibit an
Scheme 3
2
area of charge concentration (r F(r) < 0, solid lines) at
the nitrogen and carbon ends. Moreover, they have the
shape of a droplet-like appendix directed toward the osmium
atom, which is typical for a closed-shell donor-acceptor
bond.27 As expected, the newly formed ring involving the
transition metal in complex 2M is characterized by the AIM
method as a five-membered cyclic species possessing one
Os-C and one Os-N bond path and one OsNC3 ring critical
point.
As stated above, the experimental data (X-ray diffraction
and NMR chemical shifts) suggest a remarkable π-character
for the Os-C and Os-N bonds. Interestingly, the computed
ellipticities (εc) by the AIM method, which are a measure
of the double-bond character of a bond,28 indicate that
both bonds exhibit a clear π-bonding, being higher in the
Os-C bond than in the Os-N bond (εc Os-C = 0.87 and εc
Os-N = 0.48). A similar conclusion can be derived from the
second-order perturbation theory of the NBO method which
shows a higher electronic delocalization from the dπ atomic
orbital of the osmium to the π*(C-C) molecular orbital
Complex 6 was separated from the mixture as an orange
solid in 13% yield and characterized by elemental analysis,
1
IR, and H, 31P{1H}, and 13C{1H} NMR spectroscopy. In
agreement with 3 and 4, the 31P{1H} NMR spectrum shows a
1
singlet at 0.3 ppm. In the H NMR spectrum the hydride
ligands display an ABX2 spin system (X = 31P) centered at
-7.53 ppm and defined by Δν = 25 Hz, JA-B = 12.2 Hz, and
JA-X = JB-X = 15.4 Hz. In the 13C{1H} NMR spectrum the
inequivalent metalated carbon atoms of the polycycle give
rise to two triplets at 181.4 and 174.9 ppm with C-P coupling
constants of 6.8 and 7.1 Hz, respectively.
(associated second-order energy of 7.4 kcal mol-1) than to
3
the corresponding π*(N-C) molecular orbital (associated
second-order energy of 5.6 kcal mol-1).
3
The examination of the Kohn-Sham molecular orbitals
agrees with this description. As readily seen in Figure 7,
which shows the most relevant π-orbitals of the Cs-sym-
metric compound 2M, the main π-bonding interaction
between the phenyl-pyrimidine fragment and the metal
moiety occurs in the 13a00 (bonding combination) and 16a00
(“antibonding” combination) molecular orbitals. The d con-
tributions are 17% (dxz) and 41% (dyz), respectively. Strik-
ingly, in these molecular orbitals the d atomic orbitals
interact with the π-system of the metalated ring of the
phenyl-pyrimidine ligand. However, the other double-occu-
pied d atomic orbital, which is oriented to the π-system of
the nitrogen-containing aromatic ring, practically does not
interact with the ligand and remains as the nonbonding
orbital 15a00.
The 31P{1H}, 1H, and 13C{1H} NMR spectra of complex 7
agree well with those of octacycle 5. The 31P{1H} NMR
1
spectrum contains a singlet at 2.4 ppm. In the H NMR
spectrum, the hydride resonances appear at -7.40 and
-8.87 ppm as double triplets with a H-H coupling constant
of 11.0 Hz and H-P coupling constants of 21.8 and 23.8 Hz,
respectively. In the 13C{1H} NMR spectrum, the resonances
due to the metalated carbon atoms of the polycycle are
observed at 178.6 and 169.7 ppm as triplets with C-P
coupling constants of 7.2 and 6.7 Hz, respectively.
2. Bonding Situations of the New Osmapolycyclic Complexes.
Chart 2 presents the BP86/def2-SVP-optimized geometries of the
complexes 2M, 3M, and 5M, which are used as models of 2; 3, 4,
and 6; and 5 and 7, respectively. The geometrical parameters
calculated for 2M show a reasonably good agreement with those
obtained for 2 by X-ray diffraction analysis. The structural
parameters of 3M agree with those of 3 and 4, whereas the
structural parameters of 5M are consistent with those of 5. The
major deviations between experimental and computational data
are found in the donor-acceptor bonds, which may become
shorter in the solid state.24 Therefore, the selected BP86/def2-SVP
method is accurate enough to accomplish the aim of our study.
In order to analyze the bonding situations in complexes
2-7 in more detail, the nature of the bonding interactions of
Similarly, the π-molecular orbitals of the other model
complexes 2M0, 3M, and 5M show nearly identical features
as those of complex 2M (Figure 8). We can therefore con-
clude that the newly synthesized osmium-containing poly-
cycles present quite similar bonding situations, namely, a
high degree of π-character of the respective Os-C and Os-N
bonds, with the former bond possessing a higher double-
bond character as seen from the experimental data.
Conclusion
This study has revealed that the hexahydride complex
OsH6(PiPr3)2 activates ortho-CH bonds of phenyl substitu-
ents of 4,5-dimethyl-2,6-bis(4-methylphenyl)pyrimidine,
(24) Jonas, V.; Frenking, G.; Reetz, M. T. J. Am. Chem. Soc. 1994,
116, 8741.
(25) Bader, R. F. W. Atoms in Molecules. A Quantum Theory; Oxford
University Press: Oxford, 1990.
(26) (a) Foster, J. P.; Weinhold, F. J. Am. Chem. Soc. 1980, 102, 7211.
(b) Reed, A. E.; Weinhold, F. J. Chem. Phys. 1985, 83, 1736. (c) Reed, A. E.;
Weinstock, R. B.; Weinhold, F. J. Chem. Phys. 1985, 83, 735. (d) Reed,
A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899.
ꢀ
(27) Braunschweig, H.; Fernandez, I.; Frenking, G.; Radacki, K.;
Seeler, F. Angew. Chem., Int. Ed. 2007, 46, 5215, and references therein.
(28) (a) The bond ellipticity at the bond critical point is defined by the
ratio of the curvatures (eigenvalues of the Hessian of r) along the two
axes perpendicular to the bond. For details see ref 25. (b) Vyboishchikov,
S. F.; Frenking, G. Chem.;Eur. J. 1998, 4, 1428.

982 Organometallics, Vol. 29, No. 4, 2010
Chart 2. Model Compounds Studied Computationallya
Esteruelas et al.
a All structures correspond to fully optimized BP86/def2-SVP geometries. Bond lengths are given in angstroms (experimental data from X-ray in
parentheses). Unless otherwise stated, white, gray, blue, and pink colors denote hydrogen, carbon, nitrogen, and phosphorus atoms, respectively.
Figure 7. Plot of the valence π-orbitals of complex 2M (BP86/
def2-SVP level). The value of the outermost contour line is 0.035.
electronic delocalization through the polycyclic systems.
Quantum chemical calculations on model compounds sug-
gest that the Os-C and Os-N bonds of the newly formed
metallapolycycles exhibit some double-bond character that
is higher for the Os-C bond.
Experimental Section
2
Figure 6. Contour line diagrams r F(r) of the complex 2M in
the OsNC3 ring plane. Solid lines indicate areas of charge
2
concentration (r F(r) < 0), while dashed lines show areas of
2
charge depletion (r F(r) > 0). The solid lines connecting the
atomic nuclei are the bond paths. The solid lines separating
the atomic basins indicate the zero-flux surfaces crossing the
molecular plane.
General Information. All reactions were carried out with
rigorous exclusion of air using Schlenk-tube techniques. Sol-
vents (except methanol, which was dried and distilled under
argon) were obtained oxygen- and water-free from an MBraun
solvent purification apparatus. 1H, 31P{1H}, and 13C{1H} NMR
spectra were recorded on a Varian Gemini 2000, Bruker ARX
300 MHz, Bruker Avance 300 MHz, Bruker Avance 400 MHz,
2,4,6-tris(4-methylphenyl)-1,3,5-triazine, and 2,4,6-triphe-
nylpyrimidine to give, in addition to a 6-osmapyrimido-
[2,1-a]isoindole derivative, novel polycyclic compounds of
five and eight fused cycles, which have no counterpart in
conventional organic chemistry. The X-ray structures of four
of them prove the planarity of their cores and suggest

Article
Organometallics, Vol. 29, No. 4, 2010 983
Figure 8. Plot of the π-orbitals of complexes 2M0, 3M, and 5M (BP86/def2-SVP level). The value of the outermost contour line is 0.035.
or Bruker Avance 500 MHz instrument. 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 One or
Spectrum 100 spectrometer as Nujol mulls or neat solids.
C, H, and N analyses were carried out in a Perkin-Elmer
2400 CHNS/O analyzer. 4,5-Dimethyl-2,6-bis(4-methylphe-
nyl)pyrimidine29 and 2,4,6-triphenylpyrimidine30 were prepared
according to the general method for the one-step synthesis of
pyrimidines,30 2,4,6-tris(4-methylphenyl)-1,3,5-triazine31 was
prepared according to the method for the synthesis of
s-triazines,32 and OsH6(PiPr3)2 (1) was prepared as previously
reported.33
1/T (Eyring equation). Errors were computed by published
methods.35 The error in temperature was assumed to be 1 K;
error in k was estimated as 10%. (b) For the exchange that
takes place at high temperatures it was not possible to simulate
1
the H{31P} NMR spectra, and then we used the method of
Shanan-Atidi and Bar-Eli36 for analysis of exchange bet-
ween unequal populations. The activation energy of exchange
was calculated using eq 1, where kB = Boltzmann’s constant,
h = Planck’s constant, Tc = temperature of coalescence
(K), δν = chemical shift difference in the static spectrum (Hz),
and ΔP = difference in mole fractions of the exchanging
nuclei. For this problem the ratio is 2:1, so that ΔP = 1/3
(i.e., 2/3 - 1/3). X is evaluated as 2.0823 from Table 6.1 of
37
€
Sandstrom’s text.
Kinetic Analyses. The activation parameters for the hydride
exchanges in complex 2 were obtained as follows: (a) For the
exchange between the two hydrides located at lower fields
(i.e., the exchange of lower energy barrier) 1H{31P} spectral
simulation was employed: Experimental exchange broadened
line shapes were iteratively fit using the gNMR34 program, with
the line width in the absence of exchange fixed at the lowest
measured values. The activation parameters, ΔHq and ΔSq,
were obtained from a linear least-squares fit of ln(k/T) versus
ꢂ
ꢀ
ꢁꢀ
ꢁꢃ
kB Tc
X
ΔGq ¼ RT ln
ð1Þ
hπ δv
1 þ ΔP
Reaction of OsH6(PiPr3)2 with 4,5-Dimethyl-2,6-bis(4-methyl-
phenyl)pyrimidine (H2L1): Synthesis of Complexes 2 and 3. 4,5-
Dimethyl-2,6-bis(4-methylphenyl)pyrimidine (66 mg, 0.23 mmol)
was added to a solution of OsH6(PiPr3)2 (1) (117 mg, 0.23 mmol)
in toluene (10 mL) and heated under reflux for 32 h, changing the
color from pale yellow to dark red. The progress of the reaction
was monitored by 31P{1H} NMR spectroscopy, which showed
quantitative conversion to a 40:60 mixture of complexes 2 and 3.
After this time the mixture was cooled to room temperature
and the solvent was evaporated. Extraction of the resulting
residue with pentane allows the isolation of both complexes
in pure form: Complex 3 is extracted with pentane (15 mL),
while complex 2 remains in the residue. After drying both
portions, addition of methanol afforded red (2) and orange (3)
solids, which were washed with further portions of methanol
and dried in vacuo. Yield of complex 2: 45 mg (25%); complex 3:
65 mg (36%).
ꢀ
(29) Martınez-Alvarez, R.; Herrera Fernandez, A.; Chioua, M.;
´
ꢀ
Ramiro, P.; Villalba Vilchez, N.; Guzman Torres, F. Rapid Commun.
Mass Spectrom. 1999, 13, 2480.
ꢀ ꢀ
a Martınez, A.; Herrera Fernandez, A.; Moreno Jimenez,
´ ´
(30) Garcı
F.; Garcıa Fraile, A.; Subramanian, L. R.; Hanack, M. J. Org. Chem.
1992, 57, 1627.
´
(31) Forsberg, J. H.; Spaziano, V. T.; Klump, S. P.; Sanders, K. M.
J. Heterocycl. Chem. 1988, 25, 767.
(32) Herrera, A.; Martınez-Alvarez, R.; Ramiro, P.; Chioua, M.;
´
Chioua, R. Synthesis 2004, 503.
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(33) Aracama, M.; Esteruelas, M. A.; Lahoz, F. J.; Lopez, J. A.;
Meyer, U.; Oro, L. A.; Werner, H. Inorg. Chem. 1991, 30, 288.
(34) Budzelaar, P. H. M. gNMR, version 4.1; Ivory Soft: Englewood,
CO, 1999 (Published by Cherwell Scientific Publishing Limited, Oxford,
U.K.).
(36) Shanan-Atidi; Bar-Eli J. Phys. Chem. 1970, 74, 961.
(37) Sandstrom, J. Dynamic NMR Spectroscopy; Academic Press:
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(35) Morse, P. M.; Spencer, M. D.; Wilson, S. R.; Girolami, G. S.
Organometallics 1994, 13, 1646.
London, 1982.

984 Organometallics, Vol. 29, No. 4, 2010
Esteruelas et al.
Complex 2. Anal. Calcd for C38H64N2OsP2: C, 56.97; H,
8.05; N, 3.05. Found: C, 56.43; H, 8.23; N, 2.70. IR (neat
compound, cm-1): ν(Os-H); 2127 (w), 2090 (w); ν(CdN)
-8.71 (dt, JH-H = 8.0, JH-P = 18.4, 2H, Os-H). 13C{1H} NMR
(100.63 MHz, C6D6, 293 K): δ 176.3 (t, JP-C = 8.9, Os-C),
172.6 (t, JP-C = 6.4, Os-C), 174.3, 171.9, 152.3, 141.1, 139.9, 139.7
(all s, C-arom), 148.7, 141.3, 129.1, 122.0 (all s, CH-arom), 27.2
(vt, N = 24.5, PCH(CH3)2), 22.5, 22.1 (all s, CH3), 20.2 (s,
PCH(CH3)2), 19.8 (s, PCH(CH3)2). 31P{1H} NMR (161.99
MHz, C6D6, 293 K): δ 2.5 (s).
1
ν(CdC) 1584 (m), 1546 (m). H NMR (400 MHz, C6D6, 293
K): δ 8.84 (d, JH-H = 7.2, 1H, CH-arom), 8.40 (s, 1H, CH-
arom), 7.64 (d, JH-H = 8.0, 2H, CH-arom), 7.06 (d, JH-H =
8.0, 2H, CH-arom), 6.99 (d, JH-H = 7.2, 1H, CH-arom), 3.21 (s,
3H, CH3), 2.45 (s, 3H, CH3), 2.14 (s, 3H, CH3), 2.12 (s, 3H,
CH3), 1.96 (m, 6H, PCH(CH3)2), 1.02 (dvt, JH-H = 6.8, N =
12.4, 18H, PCHCH3), 0.94 (dvt, JH-H = 6.8, N = 12.0, 18H,
Reaction of OsH6(PiPr3)2 with 1 equiv of 2,4,6-Triphenylpyri-
midine (H4L3): Synthesis of Complex 6. 2,4,6-Triphenylpyrimi-
dine (45 mg, 0.15 mmol) was added to a solution of 1 (90 mg,
0.16 mmol) in toluene (5 mL) and heated under reflux. The
solution changed from pale yellow to dark red. After 7 h, the
mixture was cooled to room temperature and the solvent was
evaporated in vacuo. Addition of pentane (2 mL) caused the
precipitation of an orange solid, which was washed with pentane
(2 ꢀ 4 mL) and then methanol (4 mL) and dried in vacuo. Yield:
20 mg (13%). 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 pentane. Anal. Calcd for
C43H64N2OsP2: C, 59.97; H, 7.49; N, 3.25. Found: C, 60.25; H,
8.49; N, 3.40. IR (neat compound, cm-1): ν(Os-H); 2147 (w);
1
PCHCH3), -8.62 (br, 2H, Os-H), -12.91 (br, 1H, Os-H). H
NMR (400 MHz, C7D8, 203 K, high-field region): δ -7.51 (br,
1H, Os-H), -9.77 (br, 1H, Os-H), -12.51 (br, 1H, Os-H).
13C{1H} NMR (100.63 MHz, C6D6, 293 K): δ 185.6 (t, JP-C
= 7.3, Os-C), 174.1, 167.7, 162.5, 142.6, 138.8, 138.7, 136.8,
119.9 (all s, C-arom), 146.2, 130.1, 129.7, 129.0, 120.7 (all s, CH-
arom), 32.6, 22.2, 21.2, 17.8 (all s, CH3), 27.6 (vt, N = 23.4,
PCH(CH3)2), 20.2 (s, PCH(CH3)2), 20.0 (s, PCH(CH3)2). 31P-
{1H} NMR (161.99 MHz, C6D6, 293 K): δ 21.4 (s). T1(min) (ms,
OsH, 400 MHz, C7D8, 273 K): 102 ( 3 (-8.62 ppm); 129 ( 3
(-12.91 ppm).
1
ν(CdN), ν(CdC); 1582 (m), 1571 (m). H NMR (400 MHz,
Complex 3. Anal. Calcd for C38H62N2OsP2: C, 57.12; H, 7.82;
N, 3.51. Found: C, 56.61; H, 7.62; N, 3.46. IR (neat compound,
cm-1): ν(Os-H) 2150 (w); ν(CdN) ν(CdC) 1583 (m), 1548 (m).
1H NMR (400 MHz, C6D6, 293 K): δ 8.69 (d, JH-H = 7.8, 1H,
CH-arom), 8.40, 8.19 (all s, 1H, CH-arom), 8.12 (d, JH-H = 8.4,
1H, CH-arom), 6.98 (d, JH-H = 8.4, 1H, CH-arom), 6.95 (d,
JH-H = 7.8, 1H, CH-arom), 2.67, 2.40, 2.39, 2.34 (all s, 3H,
CH3), 2.02 (m, 6H, PCH(CH3)2), 0.85 (dvt, JH-H = 6, N = 12.2,
18H, PCHCH3), 0.83 (dvt, JH-H = 6.4, N = 12.4, 18H,
PCHCH3), -7.78 (dt, JH-H = 12.0, JH-P = 15.2, 1H, Os-H),
-8.16 (dt, JH-H = 12.0, JH-P = 15.2, 1H, Os-H). 13C{1H}
NMR (75.445 MHz, C6D6, 293 K): δ 183.4 (t,JP-C = 6.9, Os-C),
173.9 (t, JP-C = 7.4, Os-C), 171.6, 170.2, 164.4, 145.6, 143.8, 139.4,
138.2, 116.6 (all s, C-arom), 148.1, 146.6, 130.4, 127.6, 121.8, 120.6
(all s, CH-arom), 23.4, 22.0, 21.6, 17.0 (all s, CH3), 26.8 (vt, N =
24.4, PCH(CH3)2), 19.3 (s, PCH(CH3)2), 19.3 (s, PCH(CH3)2).
31P{1H} NMR (161.99 MHz, C6D6, 293 K): δ 0.0 (s).
C6D6, 293 K): δ 8.90 (d, JH-H = 6.0, 1H, CH-arom), 8.46 (d,
JH-H = 8.8, 1H, CH-arom), 8.38 (d, JH-H = 7.2, 2H, CH-
arom), 7.92 (s, 1H, CH-arom), 7.90 (d, JH-H = 6.0, 1H, CH-
arom), 7.30-6.90 (m, 7H, CH-arom), 1.95 (m, 6H, PCH-
(CH3)2), 0.77 (dvt, JH-H = 5.8, N = 11.0, 18H, PCHCH3),
0.76 (dvt, JH-H = 6.0, N = 10.8, 18H, PCHCH3), -7.53 (ABX2
spin system, Δν = 25, JH-H = 12.2, JH-P = 15.4, 2H, Os-H).
13C{1H} NMR (100.63 MHz, C6D6, 293 K): δ 181.4 (t, JP-C
=
6.8, Os-C), 174.9 (t, JP-C = 7.1, Os-C), 174.3, 172.5, 161.9,
145.7, 137.7, 128.1 (all s, C-arom), 146.8, 146.0, 131.0, 130.6,
130.5, 128.7, 128.3, 128.1, 127.9, 126.3, 120.6, 120.1, 102.3 (all s,
CH-arom), 27.0 (vt, N = 24.6, PCH(CH3)2), 19.2 (s, PCH-
(CH3)2), 19.1 (s, PCH(CH3)2). 31P{1H} NMR (161.99 MHz,
C6D6, 293 K): δ 0.3 (s).
Reaction of OsH6(PiPr3)2 with 0.5 equiv of 2,4,6-Triphenylpyri-
midine (H4L3): Synthesis of Complex 7. 1 (100 mg, 0.19 mmol)
was added to a solution of 2,4,6-triphenylpyrimidine (30 mg,
0.10 mmol) in toluene (5 mL) and heated under reflux. The
solution changed from pale yellow to dark red. After 21 h, the
mixture was cooled to room temperature and the solvent was
evaporated in vacuo. Addition of pentane (2 mL) caused the
precipitation of a red solid, which was washed with pentane (2 ꢀ
4 mL) and then methanol (4 mL) and dried in vacuo. Yield: 95 mg
(73%). Anal. Calcd for C61H106N2Os2P4: C, 52.82; H, 7.51; N,
2.09. Found: C, 53.66; H, 7.76; N, 1.96. IR (neat compound,
cm-1): ν(Os-H); 2221 (w), 2147 (w), 2107 (w); ν(CdC), ν(CdN);
1569 (m), 1549 (s). 1H NMR (400 MHz, C6D6, 293 K): δ 8.47 (d,
Reaction of OsH6(PiPr3)2 with 2,4,6-Tris(4-methylphenyl)-
1,3,5-triazine (H4L2): Synthesis of Complexes 4 and 5. 2,4,6-
Tris(4-methylphenyl)-1,3,5-triazine (136 mg, 0.38 mmol) was
added to a solution of 1 (200 mg, 0.38 mmol) in toluene (10 mL)
and heated under reflux. After 48 h, the resulting dark red
solution was cooled to room temperature and the solvent was
evaporated in vacuo. The obtained residue was extracted with
diethyl ether (25 mL), getting a dark red solution that was taken
to dryness. 1H and 31P{1H} NMR spectra of this residue in C6D6
show the presence of two complexes (4 and 5) in a ratio 8:1.
Complex 4 could be isolated as a pure red solid by addition of
methanol.
JH-H = 7.6, 2H, CH-arom), 7.92 (d, JH-H = 7.4, 2H, CH-arom),
Complex 4. Yield: 86 mg (26%). Anal. Calcd for C42H63N3OsP2:
C, 58.51; H, 7.36; N, 4.87. Found: C, 58.23; H, 7.58; N, 4.61. IR
(neat compound, cm-1): ν(Os-H); 1892 (w); ν(CdC), ν(CdN);
1584 (m), 1537 (m). 1H NMR (400 MHz, C6D6, 293 K): δ 9.19 (d,
7.77 (d, JH-H = 7.2, 2H, CH-arom), 8.19 (s, 1H, CH-arom), 7.62
(t, JH-H = 4.8, 2H, CH-arom), 7.02 (t, JH-H = 7.6, 2H, CH-
arom), 6.78 (t, JH-H = 7.2, 1H, CH-arom), 2.08 (m, 12H,
PCH(CH3)2), 0.918 (dvt, JH-H = 6.6, N = 13.0, 36 H,
PCHCH3), 0.85 (dvt, JH-H = 6.4, N = 12.4, 36 H, PCHCH3),
-7.40 (dt, JH-H = 11.0, JH-P = 21.8, 2H, Os-H), -8.87 (dt,
JH-H = 8.0, 2H, CH-arom), 9.19 (d, JH-H = 7.6, 2H, CH-arom),
8.31 (s, 2H, CH-arom), 7.21 (d, JH-H = 8.0, 2H, CH-arom), 7.07
(d, JH-H = 7.6, 2H, CH-arom), 2.39 (s, 6H, CH3), 2.14 (s, 3H,
CH3), 1.90 (m, 6H, PCH(CH3)2), 0.75 (dvt, JH-H = 6.6, N = 12.6,
36H, PCHCH3),-7.30 (t, JH-P = 15.6, 2H, Os-H).13C{1H} NMR
(100.63 MHz, C6D6, 293 K): δ 179.4 (t, JP-C = 6.8, Os-C), 177.9,
169.9, 142.6, 141.5, 141.1, 134.4 (all s, C-arom), 147.4, 129.9, 129.3,
229.2, 122.2 (all s, CH-arom), 26.9 (vt, N = 24.8, PCH(CH3)2),
22.2, 21.4 (all s, CH3), 19.1 (s, PCH(CH3)2). 31P{1H} NMR (161.99
MHz, C6D6, 293 K): δ 0.0 (s).
J
H-H = 11.0, JH-P = 23.8, 2H, Os-H). 13C{1H} NMR (100.63
MHz, C6D6, 293 K): δ 178.6 (t, JP-C = 7.2, Os-C), 169.7 (t,
JP-C = 6.7, Os-C), 168.3, 156.3, 145.9, 128.4 (all s, C-arom),
147.8, 139.7, 130.5, 129.4, 127.2, 120.1, 93.5 (all s, CH-arom),
27.1 (vt, N = 24.0, PCH(CH3)2), 20.3 (s, PCH(CH3)2), 19.7
(s, PCH(CH3)2). 31P{1H} NMR (161.99 MHz, C6D6, 293 K):
δ 2.4 (s).
Structural Analysis of Complexes 2, 3, 4, and 5. Crystals suitable
for the X-ray diffraction study were obtained by cooling a solution in
pentane at 4 ꢀC (2 and 3) or by slow diffusion of methanol into
solutions of the complexes in toluene (4 and 5). X-ray data were
collected on a Bruker Smart APEX CCD (2, 3, 4) and an Oxford
Diffraction Xcalibur TS (5) using graphite-monochromated Mo KR
radiation (λ = 0.71073 A). Data were collected over the complete
Complex 5. 1H NMR (400 MHz, C6D6, 293 K): δ 8.88 (d,
JH-H = 8.0, 2H, CH-arom), 8.37, 7.65 (all s, 2H, CH-arom),
7.06 (d, JH-H = 8.0, 2H, CH-arom), 2.51 (s, 3H, CH3), 2.41(s,
6H, CH3), 2.03 (m, 12H, PCH(CH3)2), 0.91 (dvt, JH-H = 6.4,
N = 12.8, 36H, PCHCH3), 0.84 (dvt, JH-H = 6.2, N = 12.2,
36H, PCHCH3), -7.13 (dt, JH-H = 8.0, JH-P = 16.0, 2H, Os-H),

Article
Organometallics, Vol. 29, No. 4, 2010 985
Table 1. Crystal Data Collection and Refinement for 2, 3, 4, and 5
2
3
4
5
Crystal Data
formula
molecular wt
color and habit
size, mm
symmetry, space group
a, A
b, A
c, A
R, deg
β, deg
C38H64N2OsP2
801.05
C38H62N2OsP2
799.04
C42H63N3OsP2
862.09
C60H105N3Os2P4 C4H10
3
1446.87
dark orange, prism
0.12,0.06,0.06
monoclinic, P2(1)/c
19.939(6)
16.984(5)
11.087(3)
90
93.605(5)
90
3747.3(18)
4
1.420
orange, prism
0.08,0.05,0.03
triclinic, P1
10.724(3)
11.504(3)
15.107(4)
88.454(4)
77.692(4)
82.541(5)
1805.4(8)
2
orange, prism
0.14,0.06,0.04
triclinic, P1
11.5757(15)
11.7795(15)
15.744(2)
111.362(2)
91.549(2)
97.397(2)
1976.3(4)
2
purple, plate
0.21,0.12,0.02
triclinic, P1
10.6776(2)
15.1579(4)
21.7645(3)
108.752(2)
97.1420(10)
92.741(2)
3295.24(12)
2
γ, deg
V, A3
Z
Dcalc, g cm-3
1.470
1.449
1.458
Data Collection and Refinement
diffractometer
λ(Mo KR), A
monochromator
scan type
Bruker Smart APEX
Bruker Smart APEX
Bruker Smart APEX
Oxford Diffraction Xcalibur TS
0.71073
graphite oriented
ω scans
μ, mm-1
3.516
3, 58
100(2)
46 190
9298 (Rint = 0.0538)
415/3
0.0323
0.0561
0.896
P
3.648
4, 58
100(2)
16 401
8532 (Rint = 0.0567)
3.340
4, 58
100(2)
24 987
9484 (Rint= 0.0409)
456/0
0.0321
0.0667
1.034
3.990
4, 58
2θ, range deg
temp, K
150(2)
62 671
14 417 (Rint= 0.0560)
712/2
0.0308
0.0585
0.866
no. of data collect
no. of unique data
no. of params/restraints
R1a [F2 > 2σ(F2)]
wR2b [all data]
GoF
414/33
0.0439
0.0891
0.963
P
P
P
a R1(F) = ||Fo| - |Fc||/ |Fo|. b wR2(F2) = { [w(Fo2 - Fc2)2]/ w(Fo2)2]}1/2
.
sphere and were corrected for absorption by using a multiscan
method applied with the CrisAlys RED package38 for complex 5
and with the SADABS program39 for complexes 2, 3, and 4. The
structures of allcompounds weresolved by the Patterson method.
Refinement, byfull-matrixleast-squaresonF2 withSHELXL97,40
was similar for all complexes, including isotropic and subse-
quently anisotropic displacement parameters. The hydrogen
atoms (except hydride ligands) were calculated and refined using
a restricted riding model. Hydride ligands were observed in the
difference Fourier maps and refined with restrained Os-H bond
length (1.59(1) A, CSD). The pyrimidine ring of complex 3
was found to be disordered, simulating C2 symmetry about
the osmium-nitrogen axis. The disordered atoms were defined
with two moieties (50, 50), complementary occupancy factors,
isotropic atoms, and restrained geometry. In all complexes, the
highest electronic residuals were observed in close proximity of
the Os centers and make no chemical sense. Crystal data and
details of the data collection and refinement are given in Table 1.
Computational Details
All the calculations reported in this paper were obtained with the
GAUSSIAN 03 suite of programs.41 The geometries of the mole-
cules were optimized at the gradient-corrected DFT level of theory
using Becke’s exchange functional in conjunction with Perdew’s
correlation functional (BP86)42 in combination with the double-ξ
valence plus polarization def2-SVP basis set.43 Calculation of the
vibrational frequencies44 at the optimized geometries showed that
the compounds are minima on the potential energy surface.
Donor-acceptor interactions have been computed using the
natural bond orbital (NBO) method. The energies associated
with these two-electron interactions have been computed
according to the following equation:
(38) CrysAlis; RED. A program for Xcalibur CCD System X-ray
diffraction data reduction; Oxford Diffraction Ltd.: Oxford, UK, 2005.
(39) Blessing, R. H. Acta Crystallogr. 1995, A51, 33–38. SADABS:
Area-detector absorption correction; Bruker-AXS: Madison, WI, 1996.
(40) SHELXTL Package v. 6.10; Bruker-AXS: Madison, WI, 2000.
Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
2
^
ꢁ
Æφ jFjφæ
ð2Þ
ΔE
¼ -nφ
φφꢁ
ꢁ
εφ -εΦ
(41) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A.; Vreven, Jr., T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson,
G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai,
H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken,
V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev,
O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
Morokuma, K.;Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski,
V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick,
D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.;
Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu,
G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.;
Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe,
M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez,
C.; Pople, J. A. Gaussian 03, rev. D01; Gaussian, Inc.: Wallingford, CT,
2004.
^
where F is the DFT equivalent of the Fock operator and φ
and φ* are two filled and unfilled natural bond orbitals
having εφ and εφ* energies, respectively; nφ stands for the
occupation number of the filled orbital.
Acknowledgment. Financial support from the MI-
CINN of Spain (project numbers CTQ2008-00810,
(42) (a) Becke, A. D. Phys. Rev. A 1988, 38, 3098. (b) Perdew, J. P.
Phys. Rev. B 1986, 33, 8822.
(43) Weigend, F.; Alhrichs, R. Phys. Chem. Chem. Phys. 2005, 7,
3297.
(44) McIver, J. W.; Komornicki, A. K. J. Am. Chem. Soc. 1972, 94,
2625.

986 Organometallics, Vol. 29, No. 4, 2010
Esteruelas et al.
CTQ2007-67730-C02-01/BQU, and Consolider Ingenio
Supporting Information Available: X-ray analysis and crystal
structure determination, including bond lengths and angles of
compounds 3, 2, 4, and 5. Cartesian coordinates with the total
energies of the computed compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
ꢀ
2010 CSD2007-00006), the Diputacion General de Aragon
(E35), and the CAM CCG07-UCM/PPQ-2596 is acknow-
ꢀ
ꢀ
ledged. I.F. is a Ramon y Cajal Fellow. M. M.-O. thanks
the MICINN for a FPI predoctoral grant.