Facile cleavage of phenyl groups from BiPh3 in its reactions with Os3(CO)10(NCMe)2 and evidence for localization of π-bonding in a bridging benzyne ligand

Article abstract of DOI:10.1016/j.jorganchem.2013.07.027

Three new compounds were obtained from the reaction of Os ₃(CO)₁₀(NCMe)₂, 1 with BiPh₃ in a methylene chloride solution at reflux. These have been identified as Os ₃(CO)₁₀(μ₃-C₆H₄), 3, Os₃(CO)₁₀Ph(μ-η²- O=CPh), 4, and HOs₆(CO)₂₀(μ-η²-C₆H ₄)(μ₄-Bi), 6. Two other products Os₂(CO) ₈(μ-BiPh), 2, and HOs₅(CO)₁₈(μ- η²-C₆H₄)(μ₄-Bi), 5 were obtained previously from the reaction of Os₃(CO)₁₁(NCMe) with BiPh₃. Cleavage of the phenyl groups from the BiPh₃ was the dominant reaction pathway and two of the products 3 and 4 contain rings but no bismuth. Each of the new compounds was characterized structurally by single-crystal X-ray diffraction methods. Compound 3 contains a triply-bridging benzyne (C₆H₄) ligand that exhibits a pattern of alternating long and short CeC bonds that can be attributed to partial localization of the π-bonding in the C₆ ring. The localization in the π-bonding in the ring is supported by DFT calculations. Compound 4 contains a triangular cluster of three osmium atoms with a bridging benzoyl ligand and a terminally coordinated phenyl ligand. Compound 6 contains six osmium atoms divided into two groups of four and two and the two groups are linked by a spiro-bridging bismuth atom. The group of two osmium atoms contains a bridging C₆H₄ ligand. When heated, compound 4 was converted into 3 and the compound Os₃(CO)₁₀(μ- η²-O=CPh)₂, 7. Compound 7 contains two bridging benzoyl ligands.

Full text of DOI:10.1016/j.jorganchem.2013.07.027

Journal of Organometallic Chemistry 751 (2014) 475e481
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Facile cleavage of phenyl groups from BiPh3 in its reactions with
Os3(CO)10(NCMe)2 and evidence for localization of
bridging benzyne ligand
p-bonding in a
*
Richard D. Adams , Yuwei Kan, Qiang Zhang
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new compounds were obtained from the reaction of Os3(CO)10(NCMe)2, 1 with BiPh3 in a meth-
ylene chloride solution at reflux. These have been identified as Os3(CO)10 m3-C6H4), 3, Os3(CO)10Ph(
h2
O]CPh), 4, and HOs6(CO)20 -BiPh), 2, and
2-C6H4)(m4-Bi), 6. Two other products Os2(CO)8(
HOs5(CO)18
2-C6H4)(m4-Bi), 5 were obtained previously from the reaction of Os3(CO)11(NCMe) with
BiPh3. Cleavage of the phenyl groups from the BiPh3 was the dominant reaction pathway and two of the
products 3 and 4 contain rings but no bismuth. Each of the new compounds was characterized struc-
turally by single-crystal X-ray diffraction methods. Compound 3 contains a triply-bridging benzyne
(C6H4) ligand that exhibits a pattern of alternating long and short CeC bonds that can be attributed to
Received 23 May 2013
Received in revised form
4 July 2013
(
m
-
-
(
m
-
h
m
(m-h
Accepted 9 July 2013
Keywords:
Phenyl cleavage
Osmium cluster
Bismuth
partial localization of the
p-bonding in the C6 ring. The localization in the p-bonding in the ring is
supported by DFT calculations. Compound 4 contains a triangular cluster of three osmium atoms with a
bridging benzoyl ligand and a terminally coordinated phenyl ligand. Compound 6 contains six osmium
atoms divided into two groups of four and two and the two groups are linked by a spiro-bridging bis-
muth atom. The group of two osmium atoms contains a bridging C6H4 ligand. When heated, compound 4
Benzyne
was converted into 3 and the compound Os3(CO)10
(
m
-h
2-O]CPh)2, 7. Compound 7 contains two bridging
benzoyl ligands.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
fact, only one product, Os2(CO)8(m-BiPh), contained any phenyl
groups bonded to a Bi atom. Products containing phenyl groups
or ligands derived from them, such as C6H4 and PhCO, were
abundant.
In this follow up study, we have now investigated the reaction
of BiPh3 with Os3(CO)10(NCMe)2, 1. These studies have yielded yet
another new osmiumebismuth complex as well as some new
osmium carbonyl complexes containing phenyl, benzoyl and
benzyne ligands derived from the phenyl groups that were
cleaved from the BiPh3. Most interestingly, a high resolution
The cleavage of phenyl groups from the triphenylphosphine,
PPh3, in its reactions with triosmium dodecacarbonyl goes back to
some of the very first reactions of this complex that were studied
[1,2]. Cleavage of phenyl groups from AsPh3 and SbPh3 in triosmium
carbonyl complexes is also facile [3,4]. Recently, complexes con-
taining transition metalebismuth bonds have attracted attention
[5,6]. Transition metalebismuth catalysts have been shown to
exhibit high activity and selectivity for the oxidation and ammox-
idation of hydrocarbons [7e9]. We have recently reported the
synthesis of dirhenium carbonyl complexes containing SbPh2 and
BiPh2 ligands by the cleavage of phenyl rings from SbPh3 and BiPh3
structure analysis of one of the new products Os3(CO)10(m3-C6H4),
3 which contains a triply-bridging benzyne ligand shows a
distinct pattern of long and short CeC bonds around the ring of
the benzyne ligand. Molecular orbitals for 3 were obtained by
density functional theory (DFT) calculations and indicate that
this bonding pattern can be attributed to a partial localization of
in their reactions with Re2(CO)8[m-h m-H), Eq. (1)
2-C(H)]C(H)Bun](
[10]e(2) [11]. These products have been shown to be good catalysts
for the ammoxidation of 3-picoline to 3-cyanopyridine [12].
We have also shown that phenyl groups are readily cleaved
from BiPh3 in its reaction with Os3(CO)11(NCMe), Scheme 1 [13]. In
the
p-bonding in the ring which is enhanced at the shorter CeC
bonds. The results of these studies are reported herein.
* Corresponding author.
E-mail address: Adamsrd@mailbox.sc.edu (R.D. Adams).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.07.027

476
R.D. Adams et al. / Journal of Organometallic Chemistry 751 (2014) 475e481
2. Experimental section
2.2. Reactions of Os3(CO)10(NCMe)2 with BiPh3
2.1. General data
A 52.3 mg (0.0561 mmol) amount of Os3(CO)10(NCMe)2ꢀ, 1 was
dissolved in 30 mL of methylene chloride in a 100 mL three neck
flask. To this solution was added 8.3 mg (0.0187 mmol) of BiPh3. The
solution was heated to reflux for 2 h. After cooling, the solvent was
removed in vacuo, and the products were isolated by TLC by using
an 8/1 hexane/methylene chloride elution solvent mixture to yield
Reagent grade solvents were dried by the standard procedures
and were freshly distilled under nitrogen prior to use. Unless
indicated otherwise, all reactions were performed under an at-
mosphere of nitrogen. Infrared spectra were recorded on a Thermo
Nicolet Avatar 360 FT-IR spectrophotometer. 1H NMR spectra were
recorded on a Varian Mercury 300 spectrometer operating at
300.1 MHz. Mass spectral (MS) measurements were performed by a
direct-exposure probe by using electron impact ionization (EI) on a
VG 70S instrument. Os3(CO)12 was purchased from STREM. BiPh3
was purchased from Alfa Aesar and was used without further pu-
rification. Os3(CO)10(NCMe)2 was prepared according to the previ-
ously reported procedure [14]. Product separations were performed
in order of elution: 1.9 mg of pale yellow Os2(CO)8(
(2.5% yield); 1.9 mg of yellow Os3(CO)9( -CO)(m3-C6H4), 3 (3.6%
yield); 6.5 mg of orange PhOs3(CO)10
2-O]CPh), 4 (11% yield);
5.2 mg of orange HOs5(CO)18
2-C6H4)(m4-Bi) [13], 5 (8.9% yield);
m-BiPh) [13], 2
m
(m-h
(m-h
7.9 mg of HOs6(CO)20(m-h
2-C6H4)(m4-Bi), 6 (14% yield). Spectral data
for 3: IR vCO (cmꢀ1 in hexane): 2099(vw), 2082(w), 2077(w),
2060(vs), 2024(s), 2012(s), 1998(w), 1983(vw), 1844(w). 1H NMR
(CD2Cl2,
d
in ppm) at 25 ꢁC:
d
¼ 7.65 (m, 2H, C6H4), ¼ 6.72 (m, 2H,
d
C6H4). Mass Spec. EI/MS m/z. 928 (Mþ). Spectral data for 4. IR vCO
(cmꢀ1 in methylene chloride): 2111(m), 2096(w), 2059(vs), 2027(s),
ꢀ
by TLC in open air on Analtech 0.25 mm or 0.5 mm silica gel 60 A
F254 glass plates.
Scheme 1.

R.D. Adams et al. / Journal of Organometallic Chemistry 751 (2014) 475e481
477
2003(m), 1986(m), 1942(w). 1H NMR (CD2Cl2,
d
in ppm) at 25 ꢁC:
also applied with SAINTþ. An empirical absorption correction
based on the multiple measurement of equivalent reflections was
applied using the program SADABS [16]. All structures were solved
by a combination of direct methods and difference Fourier syn-
theses, and refined by full-matrix least-squares on F2 by using the
SHELXTL software package [17]. All non-hydrogen atoms were
refined with anisotropic thermal parameters. The hydride ligand in
compound 6 was refined on its positional parameters with a fixed
isotropic thermal parameter. Compound 3 crystallized in ortho-
rhombic system. The space group Pna21 was indicated by the sys-
tematic absences in the data and confirmed by the successful
solution and refinement for the structure. Efforts to solve the
structure of 3 in the alternative centrosymmetric space group Pnma
were unsuccessful. Compounds 4, 6 and 7 crystallized in mono-
clinic system. The space groups P21/c in compound 4 and P21/n for
compounds 6 and 7 were uniquely identified by the systematic
absences in the data and were subsequently confirmed by the
successful solutions and refinements for the structures in each case.
Crystal data, data collection parameters, and results of these ana-
lyses are listed in Table 1.
d
¼ 7.22e7.84 (m, 10H, Ph). EI/MS m/z. 1034 (Mþ). Spectral data for
6. IR vCO (cmꢀ1 in hexane): 2126(w), 2089(m), 2082(m), 2073(s),
2056(w), 2044(vs), 2020(m), 2015(m), 2009(m), 2850(w). 1H NMR
(CD2Cl2,
d
in ppm) at 25 ꢁC:
d
¼ 6.59e7.08 (m, 4H, C6H4), ¼ ꢀ14.54
d
(s, hydride). EI/MS m/z. 1988 (Mþ).
3. Thermal transformations of 4
A 7.4 mg (0.0072 mmol) amount of 4 was dissolved in 10 mL of
hexane in a 50 mL three neck flask. The solution was heated up to
reflux for 5 h. After cooling, the solvent was removed in vacuo, and
the products were then isolated by TLC by using a 6/1 hexane/
methylene chloride elution solvent mixture to yield in order of
elution: 0.7 mg of 3 (10.5% yield); 3.2 mg of Os3(CO)10(m-h
2-O]
CPh)2, 7 [15] (42% yield). Spectral data for 7: IR vCO (cmꢀ1 in hex-
ane): 2099(w), 2068(vs), 2048(m), 2016(vs), 2005(s), 1998(m),
1989(w), 1983(m), 1975(w), 1954(vw). Mass Spec. EI/MS m/z. 1062
(Mþ).
3.1. Crystallographic analyses
3.2. Computational details
Yellow single crystals of 3 and orange single crystals of 4 suitable
for X-ray diffraction analysis were obtained by slow evaporation of
solvent from solutions in hexane/methylene chloride solvent
mixtures at ꢀ30 ꢁC. Dark green single crystals of 6 suitable for X-ray
diffraction analyses was obtained by slow evaporation of solvent
from a solution of the pure compound in a hexane/methylene
chloride solvent mixture at room temperature. Yellow single crys-
tals of 7 suitable for X-ray diffraction analyses was obtained by slow
evaporation of solvent from solutions in hexane solvent mixtures
at ꢀ30 ꢁC. Each data crystal was glued onto the end of a thin glass
fiber. X-ray diffraction intensity data were measured by using a
Density functional theory (DFT) calculations were performed
with the Amsterdam Density Functional (ADF) suite of programs
[18] by using the PBEsol functional [19] with Slater-type valence
quadruple-
z
þ 4 polarization function, relativistically optimized
(QZ4P) basis sets for osmium and valence triple-
z
þ 2 polarization
function (TZ2P) basis sets for carbon, oxygen, and hydrogen atoms
with small frozen cores and a scalar relativistic ZORA (Zeroth-Order
Regular Approximation) correction. The molecular orbitals for 3
and their energies were determined by a geometry-optimized gas-
phase calculation that was initiated with the structure as found in
the solid state. Electron densities at the bond critical points around
the C6 ring were calculated by using the Bader Quantum Theory of
Atoms In a Molecule (QTAIM) model and the AIMAll software
package [20,21].
Bruker SMART APEX CCD-based diffractometer by using Mo K
a
ꢀ
radiation (
l
¼ 0.71073 A). The raw data frames were integrated with
the SAINT þ program by using a narrow-frame integration algo-
rithm [16]. Corrections for Lorentz and polarization effects were
Table 1
Crystallographic data for compounds 3, 4, 6 and 7.
Compound
3
4
6
7
Empirical formula
Formula weight
Crystal system
Os3O10C16H4
926.79
Orthorhombic
Os3O11C23H10
1032.91
Monoclinic
Os6BiO17C29H10
1987.48
Monoclinic
Os3O12C24H10
1060.92
Monoclinic
Lattice parameters
ꢀ
a (A)
13.9465(3)
8.9230(2)
15.2811(3)
90.00
90.00
90.00
1901.65(7)
Pna21, no.33
4
3.237
20.048
294(2)
56.06
3363
263
1.035
0.001
0.0190, 0.0326
Multi-scan
1.000/0.749
0.496
10.9741(10)
28.833(3)
8.4711(8)
90.00
110.460(2)
90.00
2511.3(4)
P21/c, no.14
4
2.732
15.200
294(2)
50.06
4429
334
1.070
0.000
0.0423, 0.0759
Multi-scan
1.000/0.703
1.369
9.6005(4)
24.3314(10)
16.4283(7)
90.00
102.0420(10)
90.00
3753.1(3)
P21/n, no.14
4
3.517
24.977
294(2)
50.06
6624
475
1.090
0.001
0.0637, 0.1201
Multi-scan
1.000/0.523
2.935
16.766(3)
9.4626(14)
16.991(3)
90
99.243(3)
90
2660.6(7)
P21/n, no.14
4
2.649
14.354
294(2)
50.06
4689
352
1.071
0.001
0.0368, 0.0793
Multi-scan
1.000/0.646
1.387
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(deg)
(deg)
(deg)
3
ꢀ
V (A )
Space group
Z value
rcalc (g/cm3)
m
(Mo Ka) (mmꢀ1
)
Temperature (K)
Qmax (ꢁ)
No. Obs. (I > 2
No. Parameters
2
s
(I))
Goodness of fit GOFa
Max. shift in cycle
Residualsa: R1; wR2
Absorption
Correction, Max/min
Largest peak in Final Diff. Map (eꢀ/A )
3
ꢀ
GOF ¼ [Shklw (rFobsr ꢀ rFcalcr)2/(ndata e nvari)]1/2
.
a
R ¼ Shkl(rrFobsr ꢀ rFcalcrr)/ShklrFobsr; Rw ¼ [Shklw(rFobsr ꢀ rFcalcr)2/ShklwF2
]
s
1/2; w ¼ 1/ 2(Fobs).
obs

478
R.D. Adams et al. / Journal of Organometallic Chemistry 751 (2014) 475e481
4. Results
Overall, the cluster has 48 valence electrons and each of the
osmium atoms achieves an 18-electron configuration in the pres-
ence of three OseOs bonds.
Five products: Os2(CO)8(
Os3(CO)10 m3-C6H4)e, 3 (3.6% yield), Os3(CO)10Ph(
(11% yield), HOs5(CO)18
2-C6H4)(m4-Bi) [13], 5 (8.9% yield) and
HOs6(CO)20
2-C6H4)(m4-Bi), 6 (14% yield) were obtained all in
m
-BiPh) [13],
2
(2.5% yield),
m-h
(
2-O]CPh), 4
(m-h
(m-h
low yields from the reaction of 1 with BiPh3 in a methylene chloride
solution at reflux for 2 h. Three of the products, 3, 4 and 6 are new
and were characterized by a combination of IR, NMR, mass spec and
single-crystal x-ray diffraction analyses. Compounds 2 and 5 were
obtained previously from the reaction of Os3(CO)11(NCMe) with
BiPh3 [13].
An ORTEP diagram of the molecular structure of 3 is shown in
Fig. 1. Compound 3 contains three osmium atoms, nine linear ter-
minal carbonyl ligands, one asymmetrical bridging carbonyl ligand
and a triply-bridging C6H4 benzyne ligand. Compound 3 is related
ꢀ
The C(1)eC(6) distance is 1.406(9) A in length. Because of the
high quality of this structure analysis, a pattern of alternating
long and short CeC bond distances observed about the C6
to the family of compounds Os3(CO)9(m3-C6H3R)-(
m
-H)2, R ¼ H, CH3,
Cl, HC2(H)Ph, that was reported by Johnson and Lewis many years
ago [22]. The primary difference between 3 and the JohnsoneLewis
compounds is that 3 has ten CO ligands and no hydride ligands,
while the JohnsoneLewis compounds have nine CO ligands and
two bridging hydride ligands. The three osmiumeosmium bond
ꢀ
ꢀ
ring, C(1)eC(2)
C(3)eC(4)
¼
1.438(9) A, C(2)eC(3)
1.405(10) A, C(4)eC(5)
¼
1.375(10) A,
ꢀ
ꢀ
¼
¼
1.361(10)
A
and
ꢀ
C(5)eC(6) ¼ 1.428(10) A, seems to be a true effect. A similar pattern
was observed for the quadruply-bridging benzyne ligand found in
the complex Ru5((
[25]. The alternating pattern observed in the structure of the ring
found in 3 can be explained by partial localizations in the
bonding in the C6 ring induced by interruption in the delocalization
of the ebonding at the C(1)eC(6) bond due to the coordination of
these atoms to the metal atoms. This occurs by utilizing the out of
plane -orbitals of the ring as illustrated by the bonding model
m-CO)2(CO)11(m3-h
3-SC12H8)-(m4-C6H4)(m5-S)
ꢀ
distances in 3 are Os(1)eOs(2) ¼ 2.8526(3) A, Os(1)eOs(3) ¼
ꢀ
ꢀ
2.7631(4) A and Os(2)eOs(3) ¼ 2.7506(4) A in length. By contrast,
pe
Os3(CO)9(m3-C6H4)-(
m-H)2 has two long OseOs bonds, 3.026(2)
ꢀ
[3.041(2)] Å, 2.866(2) [2.849(2)] A and one shorter one, 2.751(2)
p
ꢀ
[2.751(2)] A [20]. The two long bonds in Os3(CO)9(m3-C6H4)-(m-H)2
can be attributed to effects of the hydride ligands that bridge those
p
bonds [23]. The bridging carbonyl ligand in 3, C(14)eO(14), is
shown in structure A. This idea was supported by geometry-
optimized density functional theory (DFT) calculations that were
performed on the structure of 3. Two of the key molecular orbitals
in 3, the HOMO and the HOMO-2, are shown in Fig. 2. They display a
ꢀ
slightly asymmetrically coordinated, Os(1)eC(14) ¼ 2.104(8) A,
ꢀ
Os(2)eC(14) ¼ 2.243(7) A. The formal CeC triple bond of the ben-
zyne ring in 3 is coordinated in the di-
that is well established for triply-bridging alkyne ligands [24].
s p parallel coordination A
þ
clear pattern of enhanced
p-bonding between the two pairs of
Formally, the benzyne ligand in 3 serves as a 4-electron donor.
atoms, C(2)eC(3) and C(4)eC(5), which exhibit the shortest of the
CeC ring bond distances. Selected bond distances obtained from
the crystal structure determination are compared with the corre-
sponding values obtained from the geometry-optimized DFT cal-
culations in Table 2. The correspondence is very high and supports
the above analysis. In addition, we have calculated the electron
densities at the bond critical points around the C6 ring by using
Bader’s Quantum Theory of Atoms In Molecule (QTAIM) [20].
These results are shown in Fig. 3. The calculated electron
densities are highest between the two shorter CeC ring bonds,
C(2)eC(3) ¼ 0.3182 eꢀ/bohr3 and C(4)eC(5) ¼ 0.3172 eꢀ/bohr3
which is consistent with the notion of an increase in bond locali-
zation at these two bonds.
Fig. 1. An ORTEP diagram of the molecular structure of Os3(CO)9(m-CO)(m3-C6H4), 3
showing 40% thermal ellipsoid probability. The hydrogen atoms are omitted for clarity.
ꢀ
Selected interatomic bond distances (A) are as follow: Os(1)eOs(2)
¼
2.8526(3),
2.119(8),
2.316(7),
1.406(9),
1.405(10),
Os(1)eOs(3)
Os(3)eC(1)
Os(1)eC(14)
C(1)eC(2)
¼
2.7631(4), Os(2)eOs(3)
2.335(6), Os(2)eC(6)
2.104(8), Os(2)eC(14)
¼
2.7506(4), Os(1)eC(1)
2.121(7), Os(3)eC(6)
2.243(7), C(1)eC(6)
¼
¼
¼
¼
¼
¼
¼
¼
1.438(9), C(2)eC(3)
¼
1.375(10), C(3)eC(4)
¼
Fig. 2. Molecular Orbital Diagrams of the HOMO and HOMO-2 with their energies for
compound 3 showing the p-bonding in the C6H4 ring.
C(4)eC(5) ¼ 1.361(10), C(5)eC(6) ¼ 1.428(10).

R.D. Adams et al. / Journal of Organometallic Chemistry 751 (2014) 475e481
479
Table 2
Selected bond distances for 3 from X-ray and geometry-optimized DFT
calculations.
ꢀ
ꢀ
Atoms
Distance A (X-ray)
Distances A (DFT)
Os1eOs2
Os2eOs3
Os1eOs3
C1eC2
C2eC3
C3eC4
C4eC5
C5eC6
C1eC6
2.8526(3)
2.7506(4)
2.7631(4)
1.438(9)
1.375(10)
1.405(10)
1.361(10)
1.428(10)
1.406(9)
2.834
2.778
2.775
1.425
1.377
1.413
1.377
1.425
1.438
An ORTEP diagram of the molecular structure of 4 is shown in
Fig. 4. Compound 4 contains three osmium atoms, ten CO ligands,
one of which is a semi-bridging CO ligand, and two phenyl rings;
one of which is
s-bonded to one of the osmium atoms and the
other is bonded to a CO group in the form of a bridging benzoyl
ligand. The three metal atoms are arranged in a triangle with three
ꢀ
OseOs bonds: Os(1)eOs(2) ¼ 2.8141(7) A, Os(1)eOs(3) ¼ 2.9020(6)
ꢀ
ꢀ
A, Os(2)eOs(3) ¼ 2.8606(7) A. The shortest Os(1)eOs(2) bond is the
one that contains the semi-bridging CO ligand C(11)eO(11) and the
bridging benzoyl ligand: Os(2)eC(1)
Fig. 4. An ORTEP diagram of the molecular structure of Os3(CO)10Ph(
m
-h
2-O]CPh), 4
ꢀ
¼
2.087(11) A, Os(1)e
showing 30% thermal ellipsoid probability. The hydrogen atoms are omitted for
ꢀ
ꢀ
O(1) ¼ 2.129(7) A and C(1)eO(1) ¼ 1.287(12) A. The phenyl ligand is
ꢀ
clarity. Selected interatomic bond distances (A) are as follow: Os(1)eOs(2) ¼ 2.8141(7),
ꢀ
terminally coordinated to Os(1), Os(1)eC(4) ¼ 2.125(10) A. Two
Os(1)eOs(3)
C(1)eO(1)
¼
2.9020(6), Os(2)eOs(3)
1.287(12), Os(1)eO(1)
¼
2.8606(7), Os(2)eC(1)
2.129(7), Os(1)eC(4)
¼
2.087(11),
2.125(10),
other osmium carbonyl cluster complexes containing
s
-phenyl li-
¼
¼
¼
ꢀ
Os(1)eC(11) ¼ 1.957(13), Os(2)eC(11) ¼ 2.615(13).
gands, Os4(CO)15Ph(m4-Bi) with Os
e
C
ꢀ
¼
2.178(7) A and
Os5(CO)19Ph(m4-Bi) with Os e C ¼ 2.152(13) A, were obtained from
the reaction of BiPh3 with Os3(CO)11(NCMe), see Scheme 1 [13].
Leong obtained some osmium carbonyl cluster complexes con-
four and two. The two groups are bridged by a spiro-m4-Bi atom,
ꢀ
ꢀ
Os(1)eBi(1) ¼ 2.7644(12) A, Os(2)eBi(1) ¼ 2.7085(13) A, Os(5)e
taining
ligand [4].
An ORTEP diagram of the molecular structure of 6 is shown in
s-phenyl ligands by cleaving a phenyl group from a SbPh3
ꢀ
ꢀ
Bi(1) ¼ 2.7203(12) A and Os(6)eBi(1) ¼ 2.7235(13) A. Four com-
pounds containing spiro-m4-Bi atoms were obtained in the reaction
of BiPh3 in its reaction with Os3(CO)11(NCMe), Scheme 1 [13]. One of
those was the compound 5 which was also obtained in this reac-
tion. The OseBi distances in those compounds are similar to those
found in 6. The OseOs bond distances in 6 are not unusual, except
Fig. 5. Compound 6 contains six osmium atoms in two groups of
ꢀ
for the elongated Os(5)eOs(6) bond of 3.0309(13) A in the Os2
group. This bond is bridged by a hydride ligand which was located
ꢀ
and refined crystallographically, Os(5)eH(1) ¼ 1.71(19) A, Os(6)e
ꢀ
H(1) ¼ 2.01(19) A. The presence of hydride ligand explains the
longer OseOs bond length [23]. The 1H NMR spectrum of freshly
dissolved crystals of 6 exhibits a high-field resonance at
for the hydride ligand; however, a new resonance grows in at
d
¼ ꢀ14.54,
d
¼ ꢀ14.59 ppm within a matter of minutes. After about 3 h, the two
resonances become almost equal in intensity 48/52 and remain in
this ratio thereafter. We interpret this as due to the formation of a
second isomer of compound 6 which exists in equilibrium with 6
solution. Efforts to isolate, crystallize and obtain a structural char-
acterization of the isomer having the resonance at ꢀ14.59 ppm
have been unsuccessful. Compound 6 contains m-h
2-C6H4 ligand
bridging the osmium atoms in the two atom group, Os(5)e
C(1) ¼ 2.12(3), Os(6)eC(2) ¼ 2.11(3).
2-C6H4 ligands are rare, but
one was also found in the compound HOs5(CO)18 -C6H4)(m4-Bi), 5,
m-h
(
m
ꢀ
ꢀ
Os(1)-C(2) ¼ 2.110(11) A, Os(2)-C(1) ¼ 2.132(12) A which was ob-
tained from the reaction of Os3(CO)11(NCMe) with BiPh3 [13]. Leong
also obtained some examples of m-h
2-C6H4 ligands in some osmium
carbonyl cluster complexes formed by the cleavage of phenyl rings
from SbPh3 ligands [26]. Except for the CeC bond that bridges the
ꢀ
Os(5)eOs(6) bond, C(1)eC(2) ¼ 1.47(3) A, the CeC bonds in the C6
ring in 6 are all very similar in length and all are within two esti-
ꢀ
mated standard deviations of each other: C(1)eC(6) ¼ 1.38(3) A,
Fig. 3. A drawing of the structure of 3 showing the electron densities at bond critical
points in the ring of the benzyne ligand calculated by the QTAIM method by using the
DFT optimized structure.
ꢀ
ꢀ
ꢀ
C(2)eC(3) ¼ 1.41(3) A, C(3)eC(4) ¼ 1.37(4) A, C(4)eC(5) ¼ 1.39(4) A,
ꢀ
C(5)eC(6) ¼ 1.40(3) A. This indicates that, unlike the benzyne ring

480
R.D. Adams et al. / Journal of Organometallic Chemistry 751 (2014) 475e481
in 3, any localization in the
p-bonding of the benzyne ring in 6 is
much smaller than that in 3 and is probably insignificant. The
reason for this is because the interactions of the out of plane
p-
orbitals of the ring with the metal atoms in 6 are much smaller than
with those is 3. The long length of the C(1)eC(2) bond in 6 can be
explained by di-
atoms which involves significant
-bond at the formal C(1)eC(2) triple of the benzyne ligand.
The spiro-Bi atom in 6 acts as a 5-electron donor and thus all of
s
-bonding of C(1) and C(2) to the two osmium
p-back bonding to the in plane
p
the transition metal atoms in
6 formally have 18 electron
configurations.
When compound 4 was heated to reflux in hexane solvent for
5 h, it was transformed into compound 3 in 10.5% yield and the
compound Os3(CO)10(m-h
2-O]CPh)2, 7 in 42% yield. Compound 7
was obtained by Kaesz many years ago from the reaction of
Os3(CO)12 with phenyl lithium followed by the oxidation with
(Me3O)(SbCl6) or CuBr2 [15], but this molecule was never charac-
terized structurally by X-ray crystallographic methods. That has
been done in this work. An ORTEP diagram of the molecular
structure of 7 is shown in Fig. 6. Compound 7 contains a triangular
cluster of three osmium atoms with ten linear terminal carbonyl
groups and two benzoyl ligand that bridge the atoms Os(1) and
Os(2). The benzoyl ligands serve as three electron donors so the
metal atoms have a total of 50 valence electrons and thus all of the
metal atoms achieve 18-electron configurations with the existence
ꢀ
of only two OseOs bonds. These are Os(1)eOs(3) ¼ 2.8720(6) A and
ꢀ
ꢀ
Os(2)eOs(3) ¼ 2.8810(7) A. The Os(1)eOs(2) distance of 3.652(1) A
is clearly a nonbonding interaction. The two benzoyl ligands are
paired antisymmetrically such that the oxygen atom of one is
bonded to Os(1) and the oxygen atom of the other is bonded to
Fig. 6. An ORTEP diagram of the molecular structure of Os3(CO)10(m-h
2-O]CPh)2, 7
showing 30% thermal ellipsoid probability. The hydrogen atoms are omitted for clarity.
ꢀ
ꢀ
Os(2); Os(1)eO(1) ¼ 2.112(6) A, Os(2)eO(2) ¼ 2.100(7) A (Fig. 6).
ꢀ
Selected interatomic distances (A) are as follow: Os(1)ꢂOs(2)
¼
3.652(1), Os(1)e
2.086(9), C(1)e
Os(3)
O(1)
¼
2.8720(6), Os(2)eOs(3)
1.256(10), Os(1)eO(1)
¼
2.8810(7), Os(2)eC(1)
¼
¼
¼
2.112(6), Os(1)eC(14)
¼
2.091(10), C(14)e
5. Discussion
O(2) ¼ 1.296(11), Os(2)eO(2) ¼ 2.100(7).
A summary of the reactions and products obtained in this study
is shown in the Scheme 2. Five products 2e6 were formed from the
reaction of 1 with BiPh3. Compounds 5 and 6 contain spiro-m4-Bi
atoms formed by the cleavage of all of the phenyl groups from the
BiPh3. Products 3 and 4 contain the phenyl rings that were cleaved
from the BiPh3, although the ring in 3 is actually a triply-bridging
C6H4 ligand formed by the cleavage and elimination of one
hydrogen atom from a phenyl ring. A high quality structural anal-
ysis of 3 coupled with a DFT computational analysis indicates that
there is a significant degree of localization of the p-bonding in that
ring. Compound 3 was also obtained in a low yield by heating 4. It is
Fig. 5. An ORTEP diagram of the molecular structure of Os6(CO)20
(
m
-
h
2-C6H4)(m4-Bi)(
m
-H), 6 showing 30% thermal ellipsoid probability. The hydrogen atoms are omitted for
ꢀ
clarity. Selected interatomic bond distances (A) are as follow: Os(1)eOs(2) ¼ 2.9511(13), Os(1)eOs(3) ¼ 2.8875(12), Os(1)eOs(4) ¼ 2.8268(13), Os(2)eOs(3) ¼ 2.8553(13),
Os(3)eOs(4) ¼ 2.8972(13), Os(5)eOs(6) ¼ 3.0309(13), Os(1)eBi(1) ¼ 2.7644(12), Os(2)eBi(1) ¼ 2.7085(13), Os(5)eBi(1) ¼ 2.7203(12), Os(5)eH(1) ¼ 1.71(19), Os(6)eH(1) ¼ 2.01(19),
Os(6)eBi(1) ¼ 2.7235(13), Os(5)eC(1) ¼ 2.12(3), Os(6)eC(2) ¼ 2.11(3), C(1)eC(2) ¼ 1.47(3), C(1)eC(6) ¼ 1.38(3), C(2)eC(3) ¼ 1.41(3), C(3)eC(4) ¼ 1.37(4), C(4)eC(5) ¼ 1.39(4),
C(5)eC(6) ¼ 1.40(3).

R.D. Adams et al. / Journal of Organometallic Chemistry 751 (2014) 475e481
481
Scheme 2.
anticipated that 3 was formed by the elimination of benzaldehyde
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