Reaction of multifunctional molecule (Ph2P(o-C6H4)CH{double bond, long}NCH2CH2)3N with triosmium carbonyl clusters

Article abstract of DOI:10.1016/j.jorganchem.2008.04.014

Reaction of (Ph₂P(o-C₆H₄)CH{double bond, long}NCH₂CH₂)₃N with 3 equiv. of Os₃(CO)₁₀(NCMe)₂ at ambient temperature affords the triple cluster [Os₃

Full text of DOI:10.1016/j.jorganchem.2008.04.014

Journal of Organometallic Chemistry 693 (2008) 2392–2395
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Note
Reaction of multifunctional molecule (Ph2P(o-C6H4)CH@NCH2CH2)3N
with triosmium carbonyl clusters
*
Wen-Yann Yeh , Meng-Jin Yu
Department of Chemistry, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of (Ph2P(o-C6H4)CH@NCH2CH2)3N with 3 equiv. of Os3(CO)10(NCMe)2 at ambient temperature
affords the triple cluster [Os3(CO)10Ph2P(o-C6H4)CH@NCH2CH2]3N (1) through coordination of the phos-
phine and imine groups. Thermolysis of 1 in benzene leads to decarbonylation and C–H/C–N bond acti-
vation of the ligand to generate (l-H)Os3(CO)8(l3-Ph2P(o-C6H4)CH@NC@CH2) (2). The molecular
structure of 2 has been determined by an X-ray diffraction study.
Received 12 March 2008
Received in revised form 10 April 2008
Accepted 11 April 2008
Available online 15 April 2008
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Osmium cluster
Polydentate ligand
C–H bond activation
1. Introduction
CH@NCH2CH2)3N in CD2Cl2 presents a doublet resonance at
8.84 ppm for the CH–N proton and two triplets at 3.39 and
2.45 ppm for the ethylene protons, while its 31P{1H} NMR spectrum
shows a singlet at À13.02 ppm for the phosphine groups [10].
Upon coordination to the Os3 clusters, the imine CH–N proton res-
onance is shifted upfield to 8.19 ppm, and the phosphine 31P reso-
nance is shifted downfield to 15.83 ppm. The ethylene proton
resonances are split into four signals in the range 4.42–2.38 ppm,
indicating asymmetric coordination of the imine–phosphine ligand
to result in diastereotopic CH2 groups. The spectral data suggest
equivalence of the three [Os3(CO)10Ph2P(o-C6H4)CH@NCH2CH2]
units in solution likely through C3 rotations. The IR absorptions
in the carbonyl region for 1 are shifted to lower energy compared
with Os3(CO)12, consistent with the stronger net donor capability
of imine–phosphine ligands compared with CO [12].
We have previously prepared the complex Os3(CO)10Ph2P(o-
C6H4)CH@NCH2CH2(o-C5H4N) [13], which contains an imine–phos-
phine linkage analogous to 1, and the structure of which shows
that the P–N group chelates one Os atom with the bulky Ph2P
ligand in the more opened equatorial position, while the imine
group takes up an axial position. It is probable that the imine–
phosphine species in 1 adopt a similar axial-equatorial chelating
fashion. The energy-minimized configuration constructed for 1
(Fig. 1) suggests a triangular arrangement for the Os3 clusters.
It is of interest to investigate if the Os3 units can mediate rear-
rangement of the organic ligand under severe conditions. Thus, a
benzene solution of 1 was heated to reflux under dinitrogen, and
the reaction was monitored by IR until no absorptions due to the
starting compound. After purification of the products by column
chromatography, (l-H)Os3(CO)8(l3-Ph2P(o-C6H4)CH@NC@CH2) (2)
was obtained in 68% yield (based on the Os atoms) as an air-stable,
Recently, the ability of a metal cluster to organize a flexible poly-
functional ligand around it coordination sphere has led to design of
intramolecularly organized recognition sites [1–4]. In addition,
since the cluster-bonded ligand is capable of interacting with sev-
eral metal centers, it frequently displays a reactivity different from
that found in the monometallic systems [5–9]. We have prepared
the heptafunctional molecule (Ph2P(o-C6H4)CH@NCH2CH2)3N [10]
and shown its coordination chemistry with tungsten carbonyls to
generate a novel cryptand-like metallatricycle complex. Arising
from our continuous interest in the activation of organic sub-
strates by metal clusters [11], this paper reports the reaction of
(Ph2P(o-C6H4)CH@NCH2CH2)3N with triosmium carbonyl clusters
to produce a tripodal macromolecule and its thermal reactivity
leading to C–H and C–N bond activation of the ligand.
2. Results and discussion
Treatment of (Ph2P(o-C6H4)CH@NCH2CH2)3N with 3 equiv. of
Os3(CO)10(NCMe)2 in dichloromethane at ambient temperature
for 3 h results in facile substitution of the labile acetonitrile ligands
by imine–phosphine groups to afford the tripodal triple cluster
[Os3(CO)10Ph2P(o-C6H4)CH@NCH2CH2]3N (1) in 77% yield (Scheme
1) after purification by column chromatography. Compound 1
forms an air-stable, orange solid which is soluble in common
organic solvents. The 1H NMR spectrum of free (Ph2P(o-C6H4)
* Corresponding author. Tel.: +886 7 5252000x3927.
E-mail address: wenyann@mail.nsysu.edu.tw (W.-Y. Yeh).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.04.014

W.-Y. Yeh, M.-J. Yu / Journal of Organometallic Chemistry 693 (2008) 2392–2395
2393
H
α
β
N
RT
N
+ 3 Os3(CO)10(NCMe)2
N
N
Ph
P
Ph
Ph
P
Os
H
Ph
3
Os
Os
3
1
H
H
6 CO
H
N
Os
Ph
Ph
+
NH3
3
P
H
Os
Os
2
Scheme 1.
likely caused by the bridging hydride ligand which was not located
directly [14]. The Os1, Os2, and Os3 atoms are each associated with
two, three, and three terminal carbonyl ligands, respectively, with
the Os–C–O angles ranging from 174.3(9)° to 179(1)°. The phos-
phine–imine group chelates the Os1 atom with the bite angle
P1–Os1–N1 84.1(2)°. The phosphine group takes up an equatorial
site trans to the Os1–Os2 bond with P1–Os1 2.321(2) Å and
P1–Os1–Os2 157.00(7)°, while the imine N1 atom is in the axial
position with N1–Os1 2.082(8) Å and N1–Os1–C1 169.9(4)°. The
C11–N1 distance of 1.28(1) Å retains a C–N double bond character,
while the C10–N1 single bond distance is 1.46(1) Å. The C10–N1–
C11 and N1–C11–C12 angles are 123.9(8)° and 122.6(9)°, respec-
tively, in agreement with an sp2 hybridization for the N1 and
C11 atoms. The vinyl carbon C10 is r-bonded to the Os3 atom with
C10–Os3 2.105(9) Å, and the C10–C9 double bond (1.38(1) Å) is p-
bonded to the Os2 atom with the distances C10–Os2 2.268(9) Å
and C9–Os2 2.36(1) Å. The C9–C10–N1–C11 torsional angle is
54.6(2)°.
Os
Os
P
Os
N
Os
Os
N
Os
P
N
N
Os
Os
P
It is interesting that thermal decabonylation of 1 leads to three
molecules of 2 through cleavage of two b-C–H bonds and the
amine N–C bond. One molecule of NH3 should be produced con-
comitant with the reaction, though it was not confirmed experi-
mentally. Co-thermolysis of (Ph2P(o-C6H4)CH@NCH2CH2)3N and
Os3(CO)12 in methylcyclohexane solution (101 °C) also produces
2 in lower yield (38%). The transformation from 1 to 2 apparently
involves several bond breaking and H-atom migration steps, but
the details remain unclear due to lack of reaction intermediates.
Previous study showed that [13] heating the analogous complex
Os3(CO)10Ph2P(o-C6H4)CH@NCH2CH2(o-C5H4N) in toluene results
in an imine C–H bond activation to give (l-H)Os3(CO)8Ph2P
(o-C6H4)C=NCH2CH2(o-C5H4N) and an a-C–H bond activation to
give (l-H)Os3(CO)8Ph2P(o-C6H4)CH@ NCH2CH(o-C5H4N). Since the
pyridine moiety in Os3(CO)10Ph2P(o-C6H4)CH@NCH2CH2(o-C5H4N)
is capable of binding to the Os3 cluster, the geometrical factors
likely control the structure of the products.
Os
Fig. 1. Proposed configuration of 1, showing a triangular arrangement for the three
Os3 clusters.
red crystalline solid. The FAB mass spectrum of 2 displays the
molecular ion peak at m/z 1115 for 192Os. The 31P{1H} NMR spec-
trum presents a sharp singlet at À4.64 ppm for the phosphine
group. The 1H NMR spectrum shows a 15H multiplet in the range
7.81–6.90 ppm for the imine and phenyl proton resonances, two
1H singlets at 3.64 and 1.93 ppm for the methylene protons, and
a 1H doublet (JP–H = 10 Hz) at À14.54 ppm for the bridging hydride
resonance, indicating activation of the tripodal ligand by the clus-
ters upon heating. A single crystal of 2 was thus subjected to an
X-ray diffraction analysis to reveal the structure.
3. Experimental
3.1. General methods
The molecular structure of 2 is displayed in Fig. 2. The (Ph2P(o-
C6H4)CH@NCH2CH2)3N ligand has undergone a degradation reac-
tion through N–C and C–H bond activation to generate the species
Ph2P(o-C6H4)CH@NC@CH2, which can be considered as a seven-
electron donor to result in a total of 48 valence electrons for the
cluster. The metal parts are based upon a triangular array of os-
mium atoms in which the osmium-osmium bonds show substan-
tial variation, with Os1–Os2 2.8531(5) Å, Os1–Os3 2.9688(5) Å,
and Os2–Os3 2.7502(5) Å. Lengthening of the Os1–Os3 edge is
All manipulations were carried out under an atmosphere of
dinitrogen with standard Schlenk techniques. Os3(CO)10(NCMe)2
[15] and (Ph2P(o-C6H4)CH@NCH2CH2)3N [10] were prepared by lit-
erature method. Solvents were dried over appropriate reagents un-
der dinitrogen and distilled immediately before use. 1H and
31P NMR spectra were obtained on a Varian Unity INOVA-500
spectrometer. Fast-atom-bombardment (FAB) mass spectra were
recorded on a JEOL JMS-SX102A mass spectrometer. Elemental

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W.-Y. Yeh, M.-J. Yu / Journal of Organometallic Chemistry 693 (2008) 2392–2395
Fig. 2. Molecular structure of 2. The hydrogen atoms have been artificially omitted for clarity. Selected bond lengths (Å) and bond angles (°): Os1–Os2 2.8531(5), Os1–Os3
2.9688(5), Os2–Os3 2.7502(5), Os1–P1 2.321(2), Os1–N1 2.082(8), Os2–C9 2.36(1), Os2–C10 2.268(9), Os3–C10 2.105(9), C9–C10 1.38(1), C10–N1 1.46(1), N1–C11 1.28(1),
C11–C12 1.49(1), and Os1–Os2–Os3 63.96(1), Os1–Os3–Os2 59.71(1), Os2–Os1–Os3 56.34(1), Os1–P1–C17 105.8(3), Os1–P1–C18 119.0(3), Os1–P1–C24 117.5(3), P1–Os1–
N1 84.1(2), P1–Os1–Os2 157.00(7), P1–Os1–Os3 115.30(6), N1–Os1–C1 169.9(4), N1–Os1–Os2 72.9(2), N1–Os1–Os3 69.8(2), Os2–C9–C10 69.1(5), Os2–C10–C9 76.3(6), C9–
Os2–C10 34.7(3), Os2–C10–Os3 77.8(3), Os2–Os3–C10 53.7(2), Os3–Os2–C10 48.4(2), Os3–C10–C9 130.0(7), C9–C10–N1 115.6(8), C10–N1–C11 123.9(8), N1–C11–C12
122.6(9).
analyses were performed at the National Science Council Regional
Instrumentation Center at National Chen-Kung University, Tainan,
Taiwan.
the residue from dichloromethane/methanol afforded air-stable,
red crystals of (l-H)Os3(CO)8(l3-Ph2P(o-C6H4)CH@NC@CH2) (2;
18 mg, 0.016 mmol, 68% based on the Os atom). Anal. Calc. for
C
29H18NO8Os3P: C, 31.38; H, 1.63; N, 1.26. Found: C, 31.75; H,
3.2. Reaction of (Ph2P(o-C6H4)CH@NCH2CH2)3N with
1.64; N, 1.75%. MS (FAB): m/z 1115 (M+, 192Os). IR (CH2Cl2, mCO):
Os3(CO)10(NCMe)2
2068s, 2034vs, 2008s, 1992s, 1979m, 1968m, 1975sh, 1947w
cmÀ1 1H NMR (CDCl3, 23 °C): 7.81–6.90 (m, 15H, CH–N, Ph), 3.64
.
Os3(CO)10(NCMe)2 (28 mg, 0.03 mmol) and (Ph2P(o-C6H4)
CH@NCH2CH2)3N (10 mg, 0.01 mmol) were placed in an oven-
dried 50 ml Schlenk flask, equipped with a magnetic stir bar and
a rubber serum stopper. Dichloromethane (20 ml) was introduced
into the flask and the solution was stirred at room temperature for
3 h. The solution was concentrated to ca. 2 ml on a rotary evapora-
tor and then subjected to column chromatography (alumina), elut-
ing with ethyl acetate/n-hexane (1:3 v/v). The first orange band
was collected, and the solvents were removed on a rotary evapora-
tor. The residue was dissolved in dichloromethane and layered
(s, 1H), 1.93 (s, 1H, CH2), À14.54 (d, l-H, JP–H = 10 Hz) ppm.
31P{1H} NMR (CDCl3, 23 °C): À4.64 (s) ppm.
3.4. Co-thermolysis of (Ph2P(o-C6H4)CH@NCH2CH2)3N and Os3(CO)12
Os3(CO)12 (28 mg, 0.031 mmol), (Ph2P(o-C6H4)CH@NCH2CH2)3N
(36 mg, 0.037 mmol), and methylcyclohexane (20 ml) were placed
in an oven-dried 50 ml Schlenk flask, equipped with a magnetic stir
bar and a reflux condenser. The mixture was heated to reflux under
dinitrogen for 96 h under dinitrogen. The solvent was removed un-
der vacuum and the residue was subjected to column chromato-
graphy (alumina), eluting with ethyl acetate/n-hexane (1:15 v/v).
Compound 2 (13 mg, 38%) was obtained from the second red band
as the major product. The remaining several minor bands were not
characterized.
with n-pentane to afford air-stable, orange solid of [Os3(CO)10
Ph2P(o-C6H4)CH@NCH2CH2]3N (1; 27 mg, 77%). Anal. Calc. for
93H57N4O30Os9P3: C, 31.77; H, 1.63; N, 1.59. Found: C, 32.12; H,
1.70; N, 1.90%. IR (CH2Cl2, mCO): 2088 m, 2037s, 2003vs, 1979m,
1958w, 1919vw cmÀ1 1H NMR (CD2Cl2, 23 °C): 8.19 (d, 3H, JP–H
-
C
.
=
5 Hz, CH–N), 7.72–6.51 (m, 42H, Ph), 4.42 (br, 3H), 4.11 (br, 3H),
2.96 (br, 3H), 2.38 (br, 3H, CH2) ppm. 31P{1H} NMR (CD2Cl2,
23 °C): 15.83 (s) ppm.
3.5. Structure determination for 2
The crystal of 2 found suitable for X-ray analysis was mounted
in a thin-walled glass capillary and aligned on the Nonius Kappa
CCD diffractometer, with graphite-monochromated Mo Ka radia-
tion (k = 0.71073 Å). The h range for data collection is 2.13–
25.36°. Of the 20256 reflections collected for 1, 5368 reflections
were independent. All data were corrected for Lorentz and polari-
zation effects and for the effects of absorption. The structure was
solved by the direct method and refined by least-square cycles.
The non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were included but not refined. All calculations were per-
formed using the SHELXTL-97 package [16]. The data collection and
refinement parameters are presented in Table 1.
3.3. Thermolysis of 1
[Os3(CO)10Ph2P(o-C6H4)CH@NCH2CH2]3N (1; 19 mg, 0.008 mmol)
and benzene (20 ml) were placed in an oven-dried 50 ml Schlenk
flask, equipped with a magnetic stir bar and a reflux condenser.
The solution was heated to reflux under dinitrogen for 8 days, at
which point the IR spectrum showed no absorption due to the
starting compound. The solvent was removed under vacuum and
the residue was subjected to column chromatography (alumina),
eluting with ethyl acetate/n-hexane (1:15 v/v). The first red eluant
was collected and dried on a rotary evaporator. Crystallization of

W.-Y. Yeh, M.-J. Yu / Journal of Organometallic Chemistry 693 (2008) 2392–2395
2395
Table 1
Crystallographic data for 2
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Acknowledgements
We are grateful for support of this work by the National Science
Council of Taiwan. We thank Mr. Ting-Shen Kuo (National Taiwan
Normal University, Taipei) for X-ray diffraction analysis.