2264 Organometallics, Vol. 26, No. 9, 2007
Gross et al.
(Pentamethylcyclopentadienyl)tetrabromoosmium(V), (C5Me5)-
OsBr4 (3). To a solution of (C5Me5)2Os2Br4 (0.30 g, 0.31 mmol)
in dichloromethane (15 mL) was added bromine (3.0 mL, 58.2
mmol). The solution was stirred at room temperature for 3 h. The
resulting dark microcrystalline precipitate was collected by filtration
and dried under vacuum. Yield: 0.28 g (70%). Anal. Calcd for
C10H15Br4Os: C, 18.6; H, 2.34; Br, 49.6. Found: C, 18.5; H, 2.45;
Br, 49.4. MS (FD): 647 (M+), 567 (M+ - Br), 485 (M+ - Br2).
1H NMR (DMSO-d6, 22 °C): δ 10.1 (s, fwhm ) 35 Hz, C5Me5).
IR (cm-1): 2012 (w), 1474 (s), 1424 (m), 1369 (s), 1107 (w), 1077
(w), 1015 (m), 1001 (m).
18 h; over time, the solution became bright orange and a white
flocculent precipitate appeared. The solvent was removed, leaving
a sticky brown solid which was extracted with diethyl ether (3 ×
40 mL). The extracts were combined and filtered through Celite.
The filtrate was then concentrated to 5 mL and cooled to -20 °C
to afford orange crystals, which were collected by filtration. The
supernatant was removed and concentrated further to yield a second
crop. The solid was dried overnight under vacuum. Yield: 0.10 g
(33%). Anal. Calcd for C17H23BrOs: C, 41.0; H, 4.66. Found: C,
40.8; H, 4.27. Mp: 122 °C dec. MS (FD): m/z 498 [M+]. 1H NMR
(CD2Cl2): δ 0.87 (t, JHH ) 1.5 Hz, CH), 1.38 (s, C5Me5), 3.01 (t,
JHH ) 4.5 Hz, CH), 3.57 (br s, CHdCH), 3.92 (t, JHH ) 4.0 Hz,
CH2), 4.36 (br s, CHdCH). 13C{1H} NMR (CD2Cl2): δ 33.7 (s,
CH), 9.6 (s, C5Me5), 45.8 (s, CH), 48.8 (s, CHdCH), 52.3 (s, CH2),
64.4 (s, CHdCH), 91.7 (s, C5Me5). IR (cm-1): 2720 (w), 2668
(w), 1301 (m), 1264 (m), 1171 (m), 1114 (m, br), 1026 (m), 869
(w), 814 (m), 726 (w), 627 (w).
Bis(pentamethylcyclopentadienyl)tetrabromo(µ-oxo)dios-
mium(IV), (C5Me5)2Os2(µ-O)Br4 (4). To a solution of (C5Me5)2-
Os2Br4 (0.28 g, 0.29 mmol) in dichloromethane (5 mL) was added
oxygen (ca. 150 mL) via syringe. The solution was stirred at room
temperature for 0.5 h. The resulting dark microcrystalline precipitate
was collected by filtration, washed with diethyl ether (5 mL), and
dried under vacuum. Yield: 0.11 g (38%). Anal. Calcd for C20H30-
Br4OOs2: C, 24.4; H, 3.07. Found: C, 24.3; H, 3.06. MS (FD):
Crystallographic Studies.35 (C5Me5)2Os2Br4. Single crystals of
(C5Me5)2Os2Br4 (1), grown from a 1:1 mixture of tetrahydrofuran
and pentane, were mounted on glass fibers with Paratone-N oil
(Exxon) and immediately cooled to -75 °C in a nitrogen gas stream
on the diffractometer. The structure was solved using direct methods
(SHELXTL). The quantity minimized by the least-squares program
1
566 (C5Me5OsBr3), 487 (C5Me5OsBr2), 422 (C5Me5OsOBr). H
NMR (CD2Cl2): δ 2.15 (s, C5Me5). 13C{1H} NMR (CD2Cl2, 22
°C): δ 108.9 (s, C5Me5), 13.6 (s, C5Me5). IR (cm-1): 2026 (w),
1733 (w), 1500 (m), 1424 (m), 1351 (m), 1157 (w), 1078 (m), 1036
(m), 1020 (s), 952 (w), 911 (m), 605 (w), 583 (w), 535 (w), 498
(w), 426 (m).
2
2
was ∑w(Fo - Fc2),2 where w ) {[σ(Fo )]2 + (0.06P)2}-1. In the
final cycle of least squares, independent anisotropic displacement
factors were refined for the non-hydrogen atoms. Methyl hydrogen
atoms were fixed in “idealized” tetrahedral positions with C-H )
0.98 Å and were optimized by rotation about the C-C bonds.
Displacement parameters for the hydrogen atoms were set equal
to 1.2 times Ueq for the attached carbon atom.
Bis(pentamethylcyclopentadienyl)bis(µ2-phenylimido)dibro-
modiosmium(IV), (C5Me5)2Os2(µ2-NPh)2Br2 (5). To a mixture of
(C5Me5)2Os2Br4 (0.26 g, 0.27 mmol) and LiNHPh (0.05 g, 0.53
mmol) was added diethyl ether (30 mL) precooled to -78 °C. The
solution was stirred cold for 30 min and became a burgundy color.
The solution was then warmed to room temperature and became
brown. Additional LiNHPh (0.10 g, 1.0 mmol) was added, and the
solution was stirred for 2 h. The ether was removed under vacuum,
and the dark residue was extracted with ether (3 × 20 mL, 1 × 10
mL). The extracts were filtered and combined, concentrated to 20
mL, and cooled to -20 °C. The resulting small purple crystals were
collected by filtration and dried under vacuum. The product is
difficult to separate from byproducts of the reaction. Yield: 0.02
For details of the data set collected at room temperature, see the
CIF file in the Supporting Information.
(C5Me5)2Os2(µ-O)Br4. Crystals of (C5Me5)2Os2(µ-O)Br4 (4),
grown from acetone, were treated similarly. The crystal used was
twinned; the peaks in the diffraction pattern could be indexed as a
superposition of diffracted rays from two twins with identical
monoclinic cells. The two twins were related by a rotation of ∼22°
about the reciprocal b axis. The diffraction pattern of one of the
twins was considerably more intense: the estimated relative
volumes of the major and minor components were 76% and 24%.
The data used in the least-squares refinement below were taken
from the major component only. Although the reciprocal lattices
of the two components are nonsuperimposable, some of the peaks
in the two diffraction patterns accidentally coincide; this leads to
systematic errors, which are reflected in the final difference map
(see below). Systematic absences for 0k0 (k * 2n) and h0l (h + l
* 2n) were only consistent with space group P21/n; the 0k0
condition was weakly violated, probably because of the twinning,
but successful refinement confirmed the choice of space group. The
1
g (8%). MS (FD): m/z 994 [M+]. H NMR (C6D6): δ 1.43 (s,
NH), 1.46 (s, C5Me5), 6.82 (t, JHH ) 8.5, m-CH), 7.48 (t, JHH
7.3, p-CH), 8.21 (dd, JHH ) 8.5, 7.3).
)
(Pentamethylcyclopentadienyl)tris(acetonitrile)osmium(II)
Tetraphenylborate, [(C5Me5)-Os(CH3CN)3][BPh4] (6). To
(C5Me5)2Os2Br4 (0.20 g, 0.21 mmol) was added acetonitrile (30.0
mL). The resulting dark orange-brown solution was heated to reflux
for 45 min. The bright orange solution was cooled to room
temperature, and zinc dust (0.08 g 1.22 mmol) was added. The
solution was heated to reflux for an additional 5 min. The resulting
solution was filtered hot from the excess zinc, and to the bright
yellow filtrate was added NaBPh4 (0.15 g, 0.44 mmol). After the
mixture had been stirred for 30 min, the excess acetonitrile was
removed under vacuum and the residue was extracted with
dichloromethane (30.0 mL). The solution was filtered from some
white precipitate, and the filtrate was taken to dryness under vacuum
to afford a dark yellow solid. Yield: 0.24 g (74%). Anal. Calcd
structure was solved using direct methods (SHELXTL). The
2
quantity minimized by the least-squares program was ∑w(Fo
-
2
Fc2),2 where w ) {[σ(Fo )]2 + (0.0791P)2 + 81.17P}-1. In the final
cycle of least squares, independent anisotropic displacement factors
were refined for the non-hydrogen atoms, except for the oxygen
and interior ring carbon atoms, which tended to become markedly
anisotropic (the maximum and minimum principal mean square
atomic displacements differed by as much as a factor of 15);
consequently, these atoms were restrained to near-isotropic behavior
with an effective standard deviation of 0.01. Methyl hydrogen atoms
were fixed in “idealized” tetrahedral positions with C-H ) 0.98
Å and were optimized by rotation about the C-C bonds. Displace-
ment parameters for the hydrogen atoms were set equal to 1.2 times
Ueq for the attached carbon atom. The largest peak in the final
Fourier difference map (3.32 e Å-3), which was located 1.61 Å
1
for C40H44BN3Os: C, 62.6; H, 5.74. Found: C, 62.6; H, 5.58. H
NMR (CD2Cl2): δ 1.65 (s, C5Me5), 2.56 (s, MeCN). 13C{1H} NMR
(CD2Cl2): δ 4.3 (s, MeCN), 10.1 (s, C5Me5), 77.8 (s, C5Me5), 120.1
(s, MeCN). IR (cm-1): 2280 (νCN). The PF6 salt can be made
similarly, but in low yield, by substituting KPF6 for NaBPh4
(∼10%). Anal. Calcd for C16H24N3F6OsP: C, 33.6; H, 4.79; N,
3.92. Found: C, 33.7; H, 4.85; N, 3.76. NMR data are identical
with those above.
(Pentamethylcyclopentadienyl)(η4-norbornadiene)bromo-
osmium(II), (C5Me5)Os(η4-C7H8)Br (7). To a suspension of
(C5Me5)2Os2Br4 (0.30 g, 0.31 mmol) in ethanol (60 mL) was added
norbornadiene (1.0 mL, 9.27 mmol). The solution was stirred for
(35) For details of the crystallographic methods and programs used,
see: Brumaghim, J. L.; Priepot, J. G.; Girolami, G. S. Organometallics
1999, 18, 2139-2144.
Gross, Christopher L.
