Synthesis, structural characterization and solvatochromic studies of a series of Schiff base-containing triosmium alkylidyne carbonyl clusters

Article abstract of DOI:10.1016/S0022-328X(99)00091-1

A series of new Schiff base-containing triosmium alkylidyne carbonyl clusters [Os₃(μ-H)₂(CO)₉(μ₃-CNC ₅H₄CH=NC₆H₄R)] (R = H, NMe₂, SMe, CMe₃, NH

Full text of DOI:10.1016/S0022-328X(99)00091-1

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 48–57
Synthesis, structural characterization and solvatochromic studies of
a series of Schiff base-containing triosmium alkylidyne carbonyl
clusters
Wai-Yeung Wong a,*, Wing-Tak Wong b
a Department of Chemistry, Hong Kong Baptist Uni6ersity, Waterloo Road, Kowloon Tong, Hong Kong
b Department of Chemistry, The Uni6ersity of Hong Kong, Pokfulam Road, Hong Kong, Hong Kong
Received 12 December 1998
Abstract
A series of new Schiff base-containing triosmium alkylidyne carbonyl clusters [Os3(m-H)2(CO)9(m3-CNC5H4CHꢀNC6H4R)]
(R=H, NMe2, SMe, CMe3, NH2, Br, Cl, OCnH2n+1, n=1, 6, 7 or 9) have been prepared by reaction of [Os3(m-H)3(CO)9(m3-
CCl)] with one equivalent of 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of a ten-fold excess of the Schiff base ligands
NC5H4CHꢀNC6H4R at room temperature. Analogous triosmium carbonyl clusters bearing 4%-methoxy-4-stilbazole or 4-(4-ni-
trobenzyl)pyridine moiety at the apical carbon centre have also been synthesized using a similar deprotonation method. The
molecular structures of selected complexes have been established by X-ray crystallography. UV–vis spectroscopy suggests that this
class of compounds displays significant negative solvatochromic effect in an organic medium. © 1999 Elsevier Science S.A. All
rights reserved.
Keywords: Osmium; Alkylidyne; Clusters; Solvatochromism; Crystal structures
1. Introduction
Transition-metal complexes with such ligands as 4%-
alkoxy-4-stilbazoles (NC5H4CHꢀCHC6H4OR) and 4-
pyridylmethylene-4%-alkoxyanilines (NC5H4CHꢀNC6H4-
OR) represent an active area of research in view of their
interesting optical, photophysical and liquid-crystalline
properties. However, few solid-state structures of these
complexes have been reported [1].
As a continuation of a broad study of the chemistry
and properties of trinuclear alkylidyne carbonyl clusters
of the type [M3(m-H)2(CO)9(m3-CY)] (M=Ru, Os; Y=
Lewis bases) [2], we report in this article on the prepa-
ration of a series of triosmium carbonyl clusters
This class of trinuclear alkylidyne clusters has been
shown to adopt a zwitterionic formulation and display
strong negative solvatochromism [1e,f,3]. A program
was thus initiated to study the influence of different
substituents attached to the ligands with varying elec-
tronic properties on the overall characteristics of the
system. All these new compounds have been fully char-
acterized by IR, NMR and UV–vis spectroscopies and
[Os3(m-H)2(CO)9(m3-CNC5H4CHꢀNC6H4R)]
(R=H,
NMe2, SMe, CMe3, NH2, Br, Cl, OCnH2n+1, n=1, 6,
7 or 9), containing pyridyl Schiff base ligands (I) as well
as two similar complexes with 4%-methoxy-4-stilbazole
(II) or 4-(4-nitrobenzyl)pyridine (III) as the ligands.
* Corresponding author. Fax: +852-2339-7348.
E-mail address: rwywong@net1.hkbu.edu.hk (W.-Y. Wong)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00091-1

W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
49
by FAB mass spectrometry. The molecular structures
of four of them have been established by single-crystal
X-ray analyses.
2. Results and discussion
2.1. Syntheses
All the Schiff base ligands NC5H4CHꢀNC6H4R are
prepared in good yields by the condensation of 4-
pyridinecarboxaldehyde and the corresponding substi-
tuted aromatic amines [4]. The trans-stilbazole is
obtained in a reasonable yield by the Wittig reaction of
4-pyridinecarboxaldehyde
with
4-methoxybenzyl-
triphenylphosphonium chloride [5]. Triosmium alkyl-
idyne carbonyl clusters of the type [Os3(m-H)2(CO)9-
(m3-CY)] (Y=Schiff bases 1–11, 4%-methoxy-4-stilba-
zole 12 and 4-(4-nitrobenzyl)pyridine 13) are prepared
from [Os3(m-H)3(CO)9(m3-CCl)] and the corresponding
ligands according to the DBU-initiated deprotonation
method (Scheme 1) [6]. All clusters are isolated by
preparative TLC on silica and purified by recrystalliza-
tion. Complexes 1–11 are all deeply coloured reddish
brown solids, whereas complexes 12 and 13 are isolated
as bright red and orange crystalline solids, respectively.
Scheme 1.
2.2. Solution spectroscopy
Table 1
IR and FAB MS data for complexes 1–13
The formulae of all the new complexes were first
established by FAB MS, IR and 1H-NMR spectro-
scopies. Table 1 summarizes the IR and MS spectral
data for those complexes. Their IR spectra in
dichloromethane have an almost identical wCO band
pattern in the region 2200–1600 cm−1 and are reminis-
cent of other triosmium alkylidyne clusters with a simi-
lar formulation [3]. This indicates that the pyridyl
moiety coordinates to the m3-carbon atom in an upright
manner without affecting the symmetry of each
molecule. Complexes 1–13 all show molecular ion en-
velopes of high to medium intensity in the positive FAB
mass spectra, conforming to the stoichiometry of each
compound. Sequential loss of carbonyl ligands is also
observed.
Complex IR (wCO (cm−1),
FAB MS (m/z)
CH2Cl2)
Experimental Simulated
2090m, 2055vs, 2025vs, 1020 1020
1984s, 1952m, 1936m
2089m, 2054vs, 2023vs, 1063
1982s, 1950m, 1935m
1
2
1063
1066
1076
1035
1098
1054
1050
1120
1134
1162
1049
1052
3
2090m, 2055vs, 2024vs, 1066
1983s, 1950m, 1936m
4
2090m, 2055vs, 2024vs, 1076
1983s, 1951m, 1936m
5
2090m, 2055vs, 2024vs, 1035
1983s, 1951m, 1935m
6
2090m, 2055vs, 2025vs, 1098
1984s, 1951m, 1936m
The 1H-NMR spectra of all the complexes show
resonances expected for the ligands Y and the two
bridging Os–H hydrides on the cluster framework
(Table 2). The downfield displacement of the proton
NMR signals associated with the coordinated ligands in
1–13, as compared to those resonances for the corre-
sponding free ligands, suggests that the pyridyl nitrogen
is bonded to the electron-withdrawing Os3C core. Such
shifts can be as large as ca. 1.0 ppm for the proton Ha
in most cases. For each complex, both the NC5H4 and
C6H4 rings are analyzed as AA%BB% spin systems, with
two pairs of pseudo doublets of roughly equal intensi-
7
2090m, 2055vs, 2025vs, 1054
1984s, 1952m, 1936m
8
2090m, 2055vs, 2024vs, 1050
1983s, 1951m, 1936m
9
2090m, 2055vs, 2024vs, 1120
1983s, 1951m, 1935m
10
11
12
13
2089m, 2055vs, 2024vs, 1134
1982s, 1951m, 1935m
2090m, 2055vs, 2024vs, 1162
1983s, 1950m, 1935m
2088m, 2053vs, 2022vs, 1049
1981s, 1949m, 1932m
2089m, 2055vs, 2024vs, 1052
1984s, 1951m, 1935m
1
ties shown in the H-NMR spectra. As revealed by the

50
W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
Table 2
1H-NMR chemical shifts (ppm) and coupling constants (Hz) for complexes 1–13 in CD2Cl2
Complex
Ha
Hb
–CHꢀN–
Hc
Hd
Other signals
OsH
1
2
9.73
9.58
Jab 7.0
9.70
Jab 7.0
9.71
Jab 7.0
9.62
Jab 7.1
9.73
Jab 7.1
9.73
Jab 7.0
9.42
7.88
7.80
8.57(s)
8.56(s)
ꢁꢁꢁꢁꢁꢁꢁꢁꢁꢁꢁꢁ7.43 (m, C6H5)ꢁꢁꢁꢁꢁꢁꢁꢁꢁꢁꢁꢁꢂ
−18.83(s)
−18.88(s)
7.47
6.75
3.04 (s, NMe2)
2.53 (s, SMe)
1.35 (s, CMe3)
4.07 (br, NH2)
–
Jcd 8.8
7.37
Jcd 8.9
7.49
Jcd 8.7
7.37
Jcd 8.8
7.60
3
4
7.86
7.88
7.82
7.87
7.87
7.43
8.26
8.60(s)
8.60(s)
8.56(s)
8.55(s)
8.55(s)
–
7.33
−18.83(s)
−18.84(s)
−18.88(s)
−18.81(s)
−18.81(s)
−18.96(s)
−19.00(s)
7.35
5
6.73
6
7.27
Jcd 8.8
7.44
7
7.34
–
Jcd 8.9
7.60(m)
12 a
13
6.96(m)
7.24
3.86 (s, OMe)
4.07 (s, CH2)
Jab 7.1
9.53
–
7.46
Jab 6.8
Jcd 8.8
Complex
Ha
Hb
–CHꢀN–
8.50(s)
8.58(s)
8.58(s)
8.58(s)
Hc
Hd
–OCH2-
–
–(CH2)n-
–
–CH3
OsH
8
9
9.59
Jab 7.0
9.67
Jab 7.1
9.67
Jab 7.0
9.67
7.77
7.85
7.85
7.85
7.37
Jcd 9.0
7.44
Jcd 9.0
7.44
Jcd 8.9
7.44
6.90
6.97
6.97
6.97
3.77(s)
0.92(m)
0.89(m)
0.89(m)
−18.93(s)
−18.85(s)
−18.85(s)
−18.86(s)
4.01(t)
J 6.6
4.01(t)
J 6.6
4.01(t)
J 6.6
1.27–1.85
1.26–1.83
1.12–1.85
10
11
Jab 6.8
Jcd 8.8
a The two signals for the CHꢀCH protons overlap respectively with that of Hc and Hd.
1H-NMR data for the substituents R of the Schiff bases
in 1–11, there is virtually no shift in l values for these
substituents between the clusters and the free ligands.
In addition to this, the trans-stilbazole complex 12
shows a 13C-NMR signal at l 55.83 for the methoxy
group in CD2Cl2, which is more or less unchanged
compared to the value of l 55.37 for the free ligand.
In fact, they can be considered to contain polarizable
donor-p-acceptor structural motif and a less polar ex-
cited state is expected upon MLCT excitation. For
compounds 8 and 12, where only a difference in the
linking group (CHꢀN for 8, CHꢀCH for 12) is ob-
served, the electronic absorption spectral data indicate
that the low energy MLCT transition for 8 occurs at a
lower energy than that of 12. This is probably due to
2.3. Sol6atochromic studies
Table 3
As an important part of the study on the aforemen-
tioned cluster complexes, the electronic absorption
spectra of selected complexes in a range of organic
solvents with widely different polarities have been mea-
sured and the results are presented in Table 3. The
lowest energy feature in each of these complexes is
extremely solvent dependent and displays significant
negative solvatochromism. As previously reported, in-
vestigations based on molecular orbital calculations
assign this band to the metal-to-ligand charge transfer
(MLCT) transition [3a,6a]. On the other hand, the
higher energy absorptions are relatively insensitive to
changes in solvent. Such an observation strongly con-
forms to the zwitterionic formulation of these cluster
species in their electronic ground state which can be
represented by the canonical structures shown in Fig. 1.
UV–vis excitation maxima for selected complexes
Compound umax (nm) (m×10−3 (dm3 mol−1cm−1))
CH3(CH2)4- CCl4
CH3
CH2Cl2
(CH3)2CO
1
2
–
626 (8.2)
582 (8.4)
585 (23.7)
514 (19.4)
584 (5.6)
443 (6.6)
592 (15.2)
577 (11.4)
422 (13.0)
575 (4.0)
426 (4.8)
534 (6.9)
542 (7.1)
558 (15.7)
616 (19.1)
516 (21.9)
637 (5.0)
443 (5.4)
–
613 (16.9)
520 (19.5)
625 (3.3)
430 (5.1)
641 (15.4)
620 (11.7)
3
547 (5.4)
424 (6.6)
547 (14.2)
536 (9.6)
413 (11.9)
539 (4.0)
413 (4.9)
504 (7.3)
7
8
628 (12.7)
9
622 (4.3)
416 (4.8)
581 (5.2)
614 (3.8)
417 (4.3)
575 (7.7)
12

W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
51
Fig. 1. Zwitterionic formulations of the triosmium alkylidyne carbonyl clusters.
the increasing conjugation effect of the CHꢀCH
group that stabilizes the ground state of the molecule
as compared to the CHꢀN moiety. It is also worth
pointing out that the MLCT bands for the alkoxy
homologous complexes 8–11 all essentially absorb ra-
diation at similar wavelengths in the same solvents,
ring in 13, however, shows considerable twisting at
the sp3 carbon atom C(16), with the angle C(13)–
C(16)–C(17) determined to be 114(1)° and a dihedral
angle between the pyridyl and the phenyl rings of
86.8°. The nitro group, as in other aromatic organic
molecules, is characterized by the delocalization ob-
served along
although slight differences in their
apparent.
m values are
accompanied by a slight shortening of the typical
N–O bond. In this case, the bonds N(2)–O(10) and
2.4. Crystal structure analyses
,
N(2)–O(11) are, respectively 1.13(2) and 1.19(2) A
long and the angle O(10)–N(2)–O(11) is 128(3)°.
For all complexes 1–13 that were fully character-
ized by spectroscopic methods, the solid-state struc-
tures of four of them have been ascertained by X-ray
crystallography. Single crystals of 7, 8, 12 and 13
suitable for diffraction studies were grown by slow
evaporation of their respective solutions in an n-hex-
ane/CH2Cl2 solvent mixture at room temperature
(r.t.). The molecular structures of 7, 8, 12 and 13 are
depicted in Figs. 2–5, respectively, together with the
atom-numbering scheme. Relevant bond distances and
angles are listed in Tables 4–7. Each of these struc-
tures consist of a triosmium alkylidyne metal core
arrangement with the corresponding pyridyl moiety
bonded to the m3-bridging alkylidyne carbon atom.
There are three terminal carbonyl ligands on each
vertex. Essentially, the alkylidyne metal cores in these
structures show no major variations when compared
to those of other substituted pyridine analogues de-
scribed previously [3a, 6b]. The mean Os–C(alkyli-
,
dyne) distances range from 2.08(1) to 2.100(7) A. The
two bridging metal hydrides, evident from the 1H-
NMR spectra, are located using Orpen’s potential en-
ergy minimization procedures [7]. The two
hydride-bridged Os–Os bonds (mean distance
,
2.8708(9)–2.8800(5) A) are significantly longer than
the unbridged Os–Os edge (mean distance 2.7579(9)–
,
2.7706(5) A). This is consistent with the general ob-
servation that the metal–metal bond length increases
when it is bridged by a hydride atom with the metal
hydride relatively in plane with respect to the metal
triangle [8]. There are no unusual structural or bond-
ing features in the organic moieties of these com-
plexes.
The
aromatic
rings
adopt
twisted
conformations in the solid states of 7, 8 and 12, as
revealed from the non-zero dihedral angles between
them (5.5, 3.2 and 13.1°, respectively). The phenyl
Fig.
2.
Molecular
structure
of
[Os3(mH)2(CO)9(m3-
CNC5H4CHꢀNC6H4Cl)] (7) showing the atom-numbering scheme.

52
W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
4. Experimental
4.1. General procedures
None of the compounds reported is particularly air-
sensitive, but all manipulations were carried out under
an atmosphere of dry dinitrogen. Solvents were
predried and distilled from appropriate drying agents
[9]. All chemicals, except where stated, were purchased
from commercial sources and used as received. The
compounds
[Os3(m-H)3(CO)9(m3-CCl)]
[10]
and
NC5H4CHꢀNC6H4Br [1e] were prepared by literature
methods. IR spectra were recorded as CH2Cl2 solutions
on a Perkin–Elmer 1000 or Bio-Rad FTS-7 IR spec-
trometer using 0.5 mm solution cells. The 1H-NMR
spectra were recorded on a Jeol EX270 FT-NMR spec-
trometer using deuteriated solvents as lock and the
residual protons in the solvent as references. Chemical
shifts are reported downfield positive relative to SiMe4.
Mass spectra were recorded on a Finnigan MAT 95
Fig.
3.
Molecular
structure
of
[Os3(m-H)2(CO)9(m3-
CNC5H4CHꢀNC6H4OMe)] (8) showing the atom-numbering scheme.
3. Conclusions
A series of polarizable triosmium alkylidyne carbonyl
clusters containing 4-pyridylmethylene-4%-alkoxyanilines
as ligands have been synthesized and structurally char-
acterized. This family of compounds displays interest-
ing negative solvatochromism and may provide useful
information for the study of solvent effects on MLCT
bands in transition metal complexes. It is likely that
their associated charge separation and solvatochromic
properties make them an important candidate in the
field of non-linear optics. Our present work has also
demonstrated the more effective conjugation through
the CHꢀN bond in the Schiff base-containing cluster
than the CHꢀCH bridge in the stilbazole-substituted
complex, which leads to a reduction of the energy band
gap between the highest occupied molecular orbitals
(HOMO) and the lowest unoccupied molecular orbitals
(LUMO).
Fig.
4.
Molecular
structure
of
[Os3(m-H)2(CO)9(m3-
CNC5H4CHꢀCHC6H4OMe)] (12) showing the atom-numbering
scheme.

W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
53
Fig. 5. Molecular structure of [Os3(m-H)2(CO)9(m3-CNC5H4CH2C6H4NO2)] (13) showing the atom-numbering scheme.
instrument by either the electron impact (EI) or fast
atom bombardment (FAB) technique. Electronic ab-
sorption spectra were obtained with a Perkin–Elmer
Lambda UV–vis spectrophotometer. Preparative TLC
was performed in air on 1 mm Kieselgel 60 silica
plates.
4.2. Ligand syntheses
4.2.1. Schiff base ligands NC5H4CHꢀNC6H4R
A mixture of 4-pyridinecarboxaldehyde (0.03 mol)
and the respective para-substituted aniline (0.03 mol)
Table 4
,
Selected bond distances (A) and angles (°) for compound 7
,
Bond distances (A)
Os(1)–Os(2)
Os(1)–C(10)
N(1)–C(10)
C(13)–C(16)
2.8823(3)
2.091(7)
1.446(8)
1.48(2)
Os(1)–Os(3)
Os(2)–C(10)
N(2)–C(16)
Cl–C(20)
2.7664(4)
2.135(6)
1.253(9)
1.741(8)
Os(2)–Os(3)
Os(3)–C(10)
N(2)–C(17)
2.8718(3)
2.073(5)
1.40(1)
Bond angles (°)
Os(2)–Os(1)–Os(3)
Os(1)–Os(3)–Os(2)
Os(2)–C(10)–N(1)
N(2)–C(16)–C(13)
Cl–C(20)–C(19)
61.071(9)
61.457(9)
120.9(5)
119.1(9)
119.2(8)
Os(1)–Os(2)–Os(3)
Os(1)–C(10)–N(1)
Os(3)–C(10)–N(1)
C(16)–N(2)–C(17)
Cl–C(20)–C(21)
57.472(8)
131.8(4)
133.1(5)
121.2(8)
119.5(6)

54
W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
in absolute ethanol or chloroform (30 cm3) as solvent
was heated to reflux and stirred for 2 h. The Schiff
bases that separated on cooling were filtered off and
washed with cold ethanol. The crude products were
purified by repeated recrystallization from ethanol or
chloroform, with yields of 70–80%. All components of
6.72 (d, Jcd=8.8, Hd), 7.32 (d, Jcd=8.8, Hc), 7.70 (d,
Jab=6.1, Hb), 8.46 (s, CHꢀN), 8.67 (d, Jab=6.1, Ha);
M+ (m/z) 225.
R=SMe: m.p. 82–83°C; IR (Nujol, wCHꢀN) 1622
1
cm−1; H-NMR (CDCl3, J in Hz) l 2.52 (s, SMe), 7.24
(d, Jcd=8.8, Hd), 7.29 (d, Jcd=8.8, Hc), 7.75 (d, Jab=
6.1, Hb), 8.47 (s, CHꢀN), 8.75 (d, Jab=6.1, Ha); M+
(m/z) 228.
1
the series were satisfactorily characterized by IR, H-
NMR and EI MS techniques.
R=H: m.p. 68–69°C; IR (Nujol, wCHꢀN) 1621 cm−1
;
R=CMe3: m.p. 65–66°C; IR (Nujol, wCHꢀN) 1628
1
1H-NMR (CDCl3, J in Hz) l 7.32 (m, C6H5), 7.75 (d,
Jab=6.1, Hb), 8.45 (s, CHꢀN), 8.75 (d, Jab=6.1, Ha);
M+ (m/z) 182.
cm−1; H-NMR (CDCl3, J in Hz) l 1.35 (s, CMe3),
7.21 (d, Jcd=8.8, Hd), 7.46 (d, Jcd=8.8, Hc), 7.75 (d,
Jab=6.1, Hb), 8.48 (s, CHꢀN), 8.75 (d, Jab=6.1, Ha);
M+ (m/z) 238.
R=NMe2: m.p. 197–198°C; IR (Nujol, wCHꢀN) 1617
1
cm−1; H-NMR (CDCl3, J in Hz) l 2.98 (s, NMe2),
R=NH2: m.p. 197–198°C; IR (Nujol, wCHꢀN) 1617
Table 5
,
Selected bond distances (A) and angles (°) for compound 8
,
Bond distances (A)
Os(1)–Os(2)
Os(1)–C(10)
N(1)–C(10)
C(13)–C(16)
2.880(1)
2.07(2)
1.46(2)
1.46(3)
Os(1)–Os(3)
Os(2)–C(10)
N(2)–C(16)
O(10)–C(20)
2.760(1)
2.11(2)
1.25(3)
1.35(3)
Os(2)–Os(3)
Os(3)–C(10)
N(2)–C(17)
2.868(2)
2.08(2)
1.40(2)
Bond angles (°)
Os(2)–Os(1)–Os(3)
Os(1)–Os(3)–Os(2)
Os(2)–C(10)–N(1)
N(2)–C(16)–C(13)
C(20)–O(10)–C(23)
61.09(3)
61.52(3)
121(2)
118(2)
121(3)
Os(1)–Os(2)–Os(3)
Os(1)–C(10)–N(1)
Os(3)–C(10)–N(1)
C(16)–N(2)–C(17)
57.39(3)
132(1)
132(2)
124(2)
Table 6
,
Selected bond distances (A) and angles (°) for compound 12
,
Bond distances (A)
Os(1)–Os(2)
Os(1)–C(10)
N(1)–C(10)
C(17)–C(18)
2.8864(5)
2.122(8)
1.47(2)
Os(1)–Os(3)
Os(2)–C(10)
C(13)–C(16)
O(10)–C(21)
2.8736(5)
2.08(1)
1.49(1)
1.39(1)
Os(2)–Os(3)
Os(3)–C(10)
C(16)–C(17)
2.7706(5)
2.082(7)
1.32(1)
1.48(1)
Bond angles (°)
Os(2)–Os(1)–Os(3)
Os(1)–Os(3)–Os(2)
Os(2)–C(10)–N(1)
C(13)–C(16)–C(17)
C(21)–O(10)–C(24)
57.51(1)
61.48(1)
132.2(5)
123(2)
Os(1)–Os(2)–Os(3)
Os(1)–C(10)–N(1)
Os(3)–C(10)–N(1)
C(16)–C(17)–C(18)
61.02(1)
120.9(5)
131.7(7)
127(1)
115(2)
Table 7
,
Selected bond distances (A) and angles (°) for compound 13
,
Bond distances (A)
Os(1)–Os(2)
Os(1)–C(10)
N(1)–C(10)
N(2)–O(11)
2.8796(9)
2.08(1)
1.50(2)
1.19(2)
Os(1)–Os(3)
Os(2)–C(10)
N(2)–C(20)
C(13)–C(16)
2.7579(9)
2.10(1)
1.56(3)
1.53(2)
Os(2)–Os(3)
Os(3)–C(10)
N(2)–O(10)
C(16)–C(17)
2.8620(8)
2.06(1)
1.13(2)
1.56(2)
Bond angles (°)
Os(2)–Os(1)–Os(3)
Os(1)–Os(3)–Os(2)
Os(2)–C(10)–N(1)
C(13)–C(16)–C(17)
O(11)–N(2)–C(20)
60.97(3)
61.61(3)
122.0(9)
114(1)
Os(1)–Os(2)–Os(3)
Os(1)–C(10)–N(1)
Os(3)–C(10)–N(1)
O(10)–N(2)–C(20)
O(10)–N(2)–O(11)
57.42(2)
130(1)
133(1)
118(2)
128(3)
115(2)

W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
55
cm−1; 1H-NMR (CDCl3, J in Hz) l 3.76 (br, NH2), 6.72
4.3. Synthesis of [Os3(v-H)2(CO)9(v3-CY)]
(d, Jcd=8.8, Hd), 7.22 (d, Jcd=8.8, Hc), 7.72 (d, Jab=
6.1, Hb), 8.48 (s, CHꢀN), 8.71 (d, Jab=6.1, Ha); M+
(m/z) 197.
(Y=NC5H4CHꢀNC6H4R (1–11),
NC5H4CHꢀCHC6H4OMe (12) and
NC5H4CH2C6H4NO2 (13))
R=Cl: m.p. 82–83°C; IR (Nujol, wCHꢀN) 1625 cm−1
1H-NMR (CDCl3, J in Hz) l 7.16 (d, Jcd=8.8, Hd), 7.37
(d, Jcd=8.8, Hc), 7.71 (d, Jab=6.1, Hb), 8.40 (s, CHꢀN),
8.75 (d, Jab=6.1, Ha); M+ (m/z) 216.
;
The compound [Os3(m-H)3(CO)9(m3-CCl)] (87.3 mg,
0.10 mmol) and each appropriate pyridine derivative (ten
equivalents) were dissolved in CH2Cl2 (15 cm3) and a
DBU-CH2Cl2 solution (0.10 mmol) was added dropwise.
The reaction mixture was stirred at r.t. for 30 min and
subsequently concentrated under reduced pressure. In
each case, purification was accomplished by TLC using
n-hexane/CH2Cl2 (60:40, v/v) as eluent to yield the title
complexes as a reddish–brown (for 1–11), a bright red
(for 12) or an orange crystalline (for 13) solid. The
corresponding yields and Rf values are given as follows:
1: Rf=0.6, yield 39%; 2: Rf=0.5, yield 43%; 3: Rf=0.6,
yield 41%; 4: Rf=0.5, yield 35%; 5: Rf=0.4, yield 34%;
6: Rf=0.6, yield 40%; 7: Rf=0.6, yield 50%; 8: Rf=0.6,
yield 48%; 9: Rf=0.7, yield 38%; 10: Rf=0.6, yield 37%;
11: Rf=0.5, yield 35%; 12: Rf=0.6, yield 35%; 13:
Rf=0.5, yield 38%.
R=OMe: m.p. 95–96°C; IR (Nujol, wCHꢀN) 1621
cm−1; 1H-NMR (CDCl3, J in Hz) l 3.80 (s, OMe), 6.92
(d, Jcd=8.8, Hd), 7.27 (d, Jcd=8.8, Hc), 7.70 (d, Jab=
5.9, Hb), 8.42 (s, CHꢀN), 8.71 (d, Jab=5.9, Ha); M+
(m/z) 212.
R=OC6H13: m.p. 58–59°C; IR (Nujol, wCHꢀN) 1622
1
cm−1; H-NMR (CDCl3, J in Hz) l 0.91 (m, CH3),
1.32–1.85 [m, (CH2)4], 3.98 (t, J=6.6, OCH2), 6.94 (d,
Jcd=8.8, Hd), 7.28 (d, Jcd=8.8, Hc), 7.74 (d, Jab=6.1,
Hb), 8.47 (s, CHꢀN), 8.73 (d, Jab=6.1, Ha); M+ (m/z)
282.
R=OC7H15: m.p. 68–69°C; IR (Nujol, wCHꢀN) 1621
1
cm−1; H-NMR (CDCl3, J in Hz) l 0.90 (m, CH3),
1.32–1.85 [m, (CH2)5], 3.99 (t, J=6.6, OCH2), 6.94 (d,
Jcd=8.8, Hd), 7.29 (d, Jcd=8.8, Hc), 7.74 (d, Jab=5.9,
Hb), 8.48 (s, CHꢀN), 8.73 (d, Jab=5.9, Ha); M+ (m/z)
296.
5. Crystallography
R=OC9H19: m.p. 70–71°C; IR (Nujol, wCHꢀN) 1622
1
cm−1; H-NMR (CDCl3, J in Hz) l 0.89 (m, CH3),
Single crystals of suitable size and shape were chosen
and mounted on glass fibre with epoxy resin under an
optical microscope. Geometric and intensity data for 7,
8, 12 and 13 were collected on an Enraf–Nonius CAD4
diffractometer with graphite-monochromated Mo–Ka
1.29–1.85 [m, (CH2)7], 3.99 (t, J=6.5, OCH2), 6.94 (d,
Jcd=8.8, Hd), 7.29 (d, Jcd=8.8, Hc), 7.74 (d, Jab=5.9,
Hb), 8.48 (s, CHꢀN), 8.73 (d, Jab=5.9, Ha); M+ (m/z)
324.
,
radiation (u=0.71073 A) using the ꢀ−2q scan tech-
4.2.2. Trans-stilbazole ligand NC5H4CHꢀCHC6H4OMe
To the commercially available 4-methoxybenzyl-
triphenylphosphonium chloride (2.0 g, 4.77 mmol), dis-
solved in dry benzene (50 cm3), was added a 2.0 mol
dm−3 hexane solution of n-butyllithium (2.4 cm3, 4.80
mmol) at −78°C. The deep orange mixture was stirred
under N2 at −78°C for 0.5 h followed by the addition
of 4-pyridinecarboxaldehyde (0.46 cm3, 4.77 mmol). The
reaction mixture which turned pale orange was then
refluxed overnight. After filtering off most of the
triphenylphosphine oxide, the solution was evaporated
under reduced pressure to an oil. The oily residue was
then purified by alumina chromatography using benzene
as eluent to afford a mixture of the trans- and cis-isomers
of 4%-methoxy-4-stilbazole. In this case, the pure trans-
isomer was found to crystallize from the oil at −10°C
and collected as a pale yellow solid in a 40% yield (0.40
g), leaving a yellow oil consisting mainly of the cis-iso-
mer. M.p. 108–110°C; IR (KBr): 3075w, 3027w, 2963m,
2932m, 2878w, 2860w, 1734s, 1588vs, 1513vs, 1459s,
1416s, 1312s, 1284vs, 1261vs, 1215m, 1176vs 1123m,
nique. The unit cell parameters of the compounds were
determined by a least-square analysis of 25 accurately
centred reflections. Data were collected at 298 K in the
range 252q545°. All pertinent crystallographic data
are gathered in Table 8. The stability of the crystals was
monitored at regular intervals using three standard
reflections and no significant variation was observed.
Intensity data were corrected for Lorentz and polariza-
tion effects and semi-empirical absorption corrections by
the c-scan method were also applied. Scattering factors
were taken from references [11a] and anomalous disper-
sion effects [11b] were included in Fc.
The structures were solved by a combination of direct
methods (MULTAN 82) [12] and Fourier difference tech-
niques. Refinements of structure were done on F by
full-matrix least-squares analysis with all osmium and
chlorine atoms refined anisotropically until convergence
was reached. The hydrogen atoms of the organic moieties
,
were generated in their ideal positions (C–H, 0.95 A),
while all metal hydrides were estimated by potential-en-
ergy calculations [7]. All hydrogens were included in
structure factor calculations but not refined. Calculations
were performed on a MicroVax II computer using the
SDP package [13].
1
1115m, 1073m, 1025vs, 971vs, 961s, 872m, 836vs; H-
NMR (CDCl3): l 8.52 (m, 2H, aromatic H), 6.77–7.54
(m, 6H, aromatic H), 3.84 (s, 3H, OMe); M+ (m/z) 211.

56
W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
Table 8
Crystal data and data collection parameters for 7, 8, 12 and 13
7
8
12
13
Empirical formula
Molecular weight
Crystal size (mm)
Crystal system
C22H11N2ClO9Os3
1053.1
0.32×0.32×0.40
Triclinic
C
1048.6
0.22×0.24×0.28
Triclinic
P1
8.224(1)
12.825(2)
13.801(2)
66.23(2)
79.98(2)
84.38(2)
1311.2(4)
2.656
23H14N2O10Os3
C24H15NO10Os3
1047.6
0.18×0.26×0.38
Triclinic
C22H12N2O11Os3
1050.6
0.20×0.21×0.32
Monoclinic
P21/c
8.280(1)
21.080(4)
14.828(2)
90.0
95.45(2)
90.0
(
(
(
Space group
P1
P1
,
a (A)
8.199(1)
12.505(2)
13.917(2)
66.58(2)
80.29(2)
85.16(2)
1290.3(4)
2.710
8.344(1)
12.384(2)
14.055(3)
69.32(2)
85.14(2)
85.54(2)
1352.0(5)
2.573
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
U (A )
2576.4(6)
2.708
148.42
Dcalc. (g cm−3
)
Absorption coefficient (cm−1
)
149.14
145.78
141.37
Z
2
2
2
4
F(000)
948
948
948
1896
2u range (°)
Scan type
2.0–45.0
ꢀ−2q
1.08–16.48
0.65+0.35 tan q
5426
2.0–45.0
ꢀ−2q
1.08–16.48
0.55+0.35 tan q
4839
2.0–45.0
ꢀ−2q
1.08–16.48
0.80+0.35 tan q
5095
2.0–45.0
ꢀ−2q
1.08–8.24
0.65+0.35 tan q
3750
Scan speed (deg min−1 (in ꢀ))
Scan range (ꢀ deg−1
Reflections collected
)
Independent reflections
Observed reflections [Fo\3|(Fo)]
No. of parameters
5054
4343
334
p=0.05
0.031, 0.040
1.177
4604
3644
342
p=0.04
0.062, 0.081
2.391
4737
4181
168
p=0.04
0.039, 0.055
1.791
3475
2433
168
p=0.04
0.037, 0.047
1.225
Weighting scheme w=4F2o/[|2(Fo2)+p(Fo2)2]
R, Rw
Goodness-of-fit
Residual extrema in final difference map (e A
−3
,
)
1.241 to −1.783
2.731 to −2.413
1.244 to −1.661
1.175 to −0.896
J.L. Serrano, J. Organomet. Chem. 387 (1990) 103. (b) M.A.
Esteruelas, L.A. Oro, E. Sola, M.B. Ros, J.L. Serrano, J. Chem.
Soc. Chem. Commun. (1989) 55. (c) C. Bertram, D.W. Bruce,
D.A. Dunmur, S.E. Hunt, P.M. Maitlis, M. McCann, J. Chem.
Soc. Chem. Commun. (1991) 69. (d) J.P. Rourke, F.P. Fanizzi,
N.J.S. Salt, D.W. Bruce, D.A. Dunmur, P.M. Maitlis, J. Chem.
Soc. Chem. Commun. (1990) 229. (e) W.-Y. Wong, W.-T. Wong,
K.-K. Cheung, J. Chem. Soc. Dalton Trans. (1995) 1379. (f)
W.-Y. Wong, S. Chan, W.-T. Wong, J. Chem. Soc. Dalton
Trans. (1996) 2293.
6. Supplementary material
Crystallographic data (comprising hydrogen atom
coordinates, thermal parameters and full tables of
bond lengths and angles) for the structural analysis
has been deposited with the Cambridge Crystallo-
graphic Centre (Deposition Nos. 114435 to 114438).
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (Fax: +44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
[2] (a) W.T. Wong, J. Chem. Soc. Dalton Trans. (1998) 1253 and
references cited therein. (b) W.-T. Wong, W.-Y. Wong, Acta
Crystallogr. C51 (1995) 57.
[3] For example, see (a) W.-Y. Wong, S. Chan, W.-T. Wong, J.
Organomet. Chem. 493 (1995) 229. (b) W.-Y. Wong, W.-T.
Wong, J. Chem. Soc. Dalton Trans. (1995) 2831. (c) W.-Y.
Wong, W.-T. Wong, J. Chem. Soc. Dalton Trans. (1996) 1853.
[4] M. Marcos, M.B. Ros, J.L. Serrano, M.A. Esteruelas, E. Sola,
L.A. Sola, L.A. Oro, J. Barbera, Chem. Mater. 2 (1990) 748.
[5] Y. Iseki, E. Watanabe, A. Mori, S. Inoue, J. Am. Chem. Soc.
115 (1993) 7313.
[6] (a) B.F.G. Johnson, F.J. Lahoz, J. Lewis, N.D. Prior, P.R.
Raithby, W.-T. Wong, J. Chem. Soc. Dalton Trans. (1992) 1701.
(b) S. Chan, W.-Y. Wong, W.-T. Wong, J. Organomet. Chem.
474 (1994) C30.
Acknowledgements
We acknowledge The Hong Kong Baptist Univer-
sity (W.-Y. Wong) and The University of Hong Kong
(W.-T. Wong) for financial support.
[7] A.G. Orpen, J. Chem. Soc. Dalton Trans. (1980) 2509.
[8] A.P. Humphries, H.D. Kaesz, Prog. Inorg. Chem. 2 (1979) 145.
[9] W.L.F. Armarego, D.D. Perrin, Purification of Laboratory
Chemicals, 4th edn, Butterworth–Heinemann, Guildford, UK,
1996.
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W.-Y. Wong, W.-T. Wong / Journal of Organometallic Chemistry 584 (1999) 48–57
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