1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane, a highly versatile cyclocarbaphosphine ligand: Reactions with activated triosmium clusters and characterization of the products

Article abstract of DOI:10.1021/ic025589c

Reaction of 1,2,3,4-tetraphenyl-1,2,3,4-tetraphospholane (I) with [Os₃(CO)₁₁(NCMe)] at ambient temperature affords substituted clusters: the monosubstituted trinuclear cluster [Os₃(CO)₁₁{(PPh)₄CH₂}] (1) and the isomeric linked bis-trinuclear clusters [{Os₃(CO)₁₁}2{μ-1,4-η² -(PPh)₄CH₂}] (2) and [{Os₃(CO)₁₁}₂{μ-1,3-η²- (PPh)₄CH₂}] (3). Clusters 2 and 3 can also be prepared by further reaction of 1 with [Os₃(CO)₁₁(NCMe)]. The reaction at 100 °C gives, apart from cluster 2, the disubstituted 1,4-bridged trinuclear cluster [Os₃(CO)₁₀{μ-1,4-η² -(PPh)₄CH₂}] (4). The conversion of 1 into 4 can be achieved through the pyrolysis of a solution of 1. When 1 reacts with an equimolar amount of [Os₃(CO)₁₀(μ-H)₂] at 100 °C in toluene, the 1,2,4-linked bis-trinuclear cluster [Os₃(CO)₁₁{μ₃-1,2,4-η³ -(PPh)₄CH₂}-Os₃(CO)₈ (μ-H)₂] (5) is obtained. When I reacts with a 2-fold molar amount of [Os₃(CO)₁₀(μ-H)₂], the 1,2,3,4-linked bis-trinuclear hydride cluster [{Os₃(CO)₈(μ-H)₂}₂ {μ₄-1,2,3,4-η⁴-(PPh)₄CH₂}] (6) is obtained. Cluster 1 exists as two conformational isomers (1y and 1r) in the crystalline state, due to different conformational arrangements of pseudoaxial carbonyls in the cluster. Cluster 3 shows two interconvertible conformers (3y and 3r) due to the inversion of the configuration of the uncoordinated outer phosphorus atom, and a pair of enantiomers exists in 3r. All of the new compounds obtained have been characterized by spectroscopic and analytical techniques, and their structures have been established by X-ray crystallography.

Full text of DOI:10.1021/ic025589c

Inorg. Chem. 2002, 41, 3791−3800
1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane, a Highly Versatile
Cyclocarbaphosphine Ligand: Reactions with Activated Triosmium
Clusters and Characterization of the Products
Siau-Gek Ang,* Xinhua Zhong, and How-Ghee Ang
Department of Chemistry, National UniVersity of Singapore, 119260, Singapore
Received March 13, 2002
Reaction of 1,2,3,4-tetraphenyl-1,2,3,4-tetraphospholane (I) with [Os3(CO)11(NCMe)] at ambient temperature affords
substituted clusters: the monosubstituted trinuclear cluster [Os3(CO)11{(PPh)4CH }] (1) and the isomeric linked
2
bis-trinuclear clusters [{Os3(CO)11}2{µ-1,4-η2-(PPh)4CH }] (2) and [{Os3(CO)11}2{µ-1,3-η2-(PPh)4CH }] (3). Clusters
2
2
2 and 3 can also be prepared by further reaction of 1 with [Os3(CO)11(NCMe)]. The reaction at 100 °C gives, apart
from cluster 2, the disubstituted 1,4-bridged trinuclear cluster [Os3(CO)10{µ-1,4-η2-(PPh)4CH }] (4). The conversion
2
of 1 into 4 can be achieved through the pyrolysis of a solution of 1. When 1 reacts with an equimolar amount of
[Os3(CO)10(µ-H)2] at 100 °C in toluene, the 1,2,4-linked bis-trinuclear cluster [Os3(CO)11{µ3-1,2,4-η3-(PPh)4CH }-
2
Os3(CO)8(µ-H)2] (5) is obtained. When I reacts with a 2-fold molar amount of [Os3(CO)10(µ-H)2], the 1,2,3,4-linked
bis-trinuclear hydride cluster [{Os3(CO)8(µ-H)2}2{µ4-1,2,3,4-η4-(PPh)4CH }] (6) is obtained. Cluster 1 exists as
2
two conformational isomers (1y and 1r) in the crystalline state, due to different conformational arrangements of
pseudoaxial carbonyls in the cluster. Cluster 3 shows two interconvertible conformers (3y and 3r) due to the
inversion of the configuration of the uncoordinated outer phosphorus atom, and a pair of enantiomers exists in 3r.
All of the new compounds obtained have been characterized by spectroscopic and analytical techniques, and their
structures have been established by X-ray crystallography.
Introduction
have been extensively studied in recent years. In most
instances, the polyphosphine ligands undergo ring rupture
under forcing reaction conditions to afford phosphido- or
phosphinidene-substituted cluster derivatives. In cases where
the ligand ring frameworks remain intact, the ligands
normally act as mono- or bidentate ligands and adopt η1 or
µ-η2 coordination modes with clusters. Although (PEt)5 has
been proposed to act as a tridentate ligand adopting a µ3-η3
coordination mode in osmium cluster derivatives, no crystal
structures for these clusters have been reported.1e Herein we
report the reactions of 1,2,3,4-tetraphenyl-1,2,3,4-tetraphos-
pholane (I) with the activated triosmium carbonyl clusters
The reactions of homocyclopolyphosphines (PR)n (R )
Ph,1a-c Et,1c-e CF3,1f But;2 n ) 4, 5), cyclocarbaphosphines
(1,2,3-triphenyl-1,2,3-triphosphaindan,3,4 pentaphenyl-1,2,3-
triphospholene,5 and tetrakis(trifluoromethyl-1,2-diphos-
phetene6) with iron, ruthenium, and osmium carbonyl clusters
* Author to whom correspondence should be addressed. E-mail: sciangsg@
nus.edu.sg. Fax: (65)68723564.
(1) (a) Ang, H. G.; Koh, L. L.; Zhang,Q. J. Chem. Soc., Dalton Trans.
1995, 2757. (b) Ang, H. G.; Ang, S. G.; Zhang, Q. J. Chem. Soc.,
Dalton Trans. 1996, 3843. (c) Ang, H. G.; Ang, S. G.; Zhang, Q. J.
Chem. Soc., Dalton Trans. 1996, 2773. (d) Ang, H. G.; Ang, S. G.;
Kwik, W. L.; Zhang, Q. J. Organomet. Chem. 1995, 485, C10. (e)
Ang, H. G.; Ang, S. G.; Zhang, Q. Phosphorus, Sulfur Silicon Relat.
Elem. 1996, 110, 145. (f) Ang, H. G.; Aug, K. W.; Ang, S. G.;
Rheingold, A. L. J. Chem. Soc., Dalton Trans. 1996, 3131.
(2) (a) Johnson, B. F. G.; Layer, T. M.; Lewis, J.; Raithby, P. R.; Wong,
W. T. J. Chem. Soc., Dalton Trans. 1993, 973. (b) Charalambous, E.;
Heuer, L.; Johnson, B. F. G.; Lewis, J.; Li, W. S.; McPartlin, M.;
Massey, A. D. J. Organomet. Chem. 1994, 468, C9.
(3) (a) King, R. B.; Reimann, R. H. Inorg, Chem. 1976, 15, 184. (b) Kyba,
E. P.; Hassett, K. L.; Sheikh, B.; Mckennis, J. S.; King, R. B.; Davis,
R. E. Organometallics 1985, 4, 994.
(4) Ang, S. G.; Zhong, X. H.; Ang, H. G. J. Chem. Soc., Dalton Trans.
2001, 1151.
[Os3(CO)11(NCMe)] and [Os3(CO)10(µ-H)2] under various
(5) Ang, H. G.; Ang, S. G.; Wang, X. J. Chem. Soc., Dalton Trans. 2000,
3429.
(6) Cowley, A. H.; Hill, K. E. Inorg. Chem. 1973, 12, 1446.
Inorganic Chemistry, Vol. 41, No. 14, 2002 3791
10.1021/ic025589c CCC: $22.00 © 2002 American Chemical Society
Published on Web 06/19/2002

Ang et al.
was evaporated to dryness under reduced pressure. One major
compound was obtained from this residue after TLC separation
using CH2Cl2/hexane (1:3, v/v) as eluent. This was the yellow
cluster [Os3(CO)10{µ-1,4-η2-(PPh)4CH2}] (4; Rf ) 0.57, 108 mg,
42%). Anal. Found for 4: C, 32.02; H, 2.02; P, 9.14. Calcd for
C35H22O10Os3P4: C, 32.38; H, 1.69; P, 9.56.
(d) At 100 °C with a 1:2.5 Molar Ratio. The reaction conditions
were similar to those in (c). [Os3(CO)11(NCMe)] (200 mg, 0.22
mmol) was treated with I (39 mg, 0.09 mmol). Cluster 2 (Rf )
0.58, 87 mg, 45%) was obtained after TLC using CH2Cl2/hexane
(1/3) as eluent.
Reaction of Cluster 1 with [Os3(CO)11(NCMe)]. This reaction
was similar to that in (a) above. Cluster 1 (80 mg, 0.06 mmol) was
treated with [Os3(CO)10(NCMe)] (57 mg, 0.06 mmol) in dichloro-
methane (10 mL) at room temperature overnight. Clusters 2 (Rf )
0.56, 42 mg, 32%) and 3 (Rf ) 0.49, 58 mg, 45%) were obtained
after TLC using CH2Cl2/hexane (1/4) as eluent.
Conversion of Cluster 1 into 4. A single reaction vessel was
charged with cluster 1 (45 mg, 0.03 mol) in toluene (10 mL). The
solution was degassed over three freeze-pump-thaw cycles. The
tube and its contents were heated overnight in a 100 °C oil bath.
One major band was eluted (CH2Cl2/hexane (1/3)), which was
identified by 31P NMR as 4 (Rf ) 0.52, 28 mg, 74%).
conditions, where a series of new cluster derivatives with
the ligand ring framework intact are obtained. In these cluster
derivatives, I is highly versatile in its range of coordination
modes, η1, µ-1,3-η2, µ-1,4-η2, µ3-1,2,4-η3, and µ4-1,2,3,4-
η4, and acts as mono-, bi-, tri-, and tetradentate P-donor
ligands in different products, respectively. To the best of our
knowledge, very few known ligands have such a variety of
coordination modes toward the same metal cluster as
observed for the ligand I.
Experimental Section
General Procedures. All reactions involving clusters described
here were carried out in vacuo using double-tube reaction vessels
equipped with Teflon taps. The starting materials [Os3(CO)12)],
[Os3(CO)11(NCMe)], [Os3(CO)10(µ-H)2], and [(PPh)4CH2] were
prepared by literature methods.7-10 Elemental analysis was carried
out at the Microanalytical Laboratory, Department of Chemistry,
National University of Singapore. Infrared spectra were recorded
as solutions in 1 cm KBr cells on a Bio-Rad FTS-165 spectrometer,
1H and 31P NMR spectra on Bruker 300 or 500 MHz Fourier
transform spectrometers using SiMe4 (for 1H) and 85% H3PO4 (for
31P) as references, and mass spectra on a Finnigan MAT 95
instrument by the fast atom bombardment technique, using R-
nitrobenzyl alcohol or thioglycerol as the matrix solvent.
Reaction of I with [Os3(CO)11(NCMe)]. (a) At Room Tem-
perature with an Equimolar Ratio. [Os3(CO)11(NCMe)] (150 mg,
0.16 mmol) and I (73 mg, 0.16 mmol) were placed in the inner
tube of a double-tube reaction vessel and degassed under vacuum.
Freshly distilled dichloromethane (10 mL) was placed in the outer
tube of the reaction vessel. After degassing with three freeze-
pump-thaw cycles, the solvent was then transferred to the inner
tube with the reactants. The reaction system was stirred at room
temperature overnight. The resultant red solution was evaporated
to dryness under reduced pressure. The residue was dissolved in
the minimum volume of CH2Cl2 and separated by TLC using
CH2Cl2-hexane (1:4, v/v) as eluent. One major yellow band of
the cluster [Os3(CO)11{(PPh)4CH2}] (1; Rf ) 0.60, 137 mg, 65%)
was eluted and collected. Anal. Found for 1: C, 32.60; H, 1.66; P,
8.90. Calcd for C36H22O11Os3P4: C, 32.62; H, 1.66; P, 9.35.
(b) At Room Temperature with a 1:2.5 Molar Ratio. The
reaction conditions were similar to that of (a). [Os3(CO)11(NCMe)]
(200 mg, 0.22 mmol) reacted with (I) (39 mg, 0.09 mmol) in
CH2Cl2 (10 mL) at room-temperature overnight to afford a red
solution and some yellow precipitate. On filtering off the precipitate,
the filtrate was analyzed by TLC chromatography using CH2Cl2/
hexane (1:3, v/v) as eluent to afford two major bands of cluster
[{Os3(CO)11}2{µ-1,4-η2-(PPh)4CH2}] 2 (Rf ) 0.57, 40 mg (together
with the precipitate), 21% (based on ligand and the same for 3),
and cluster [{Os3(CO)11}2{µ-1,3-η2-(PPh)4CH2}] (3; Rf ) 0.51, 73
mg, 38%). The precipitate was identified as the same compound
as band 1 from the filtrate. Anal. Found for 2: C, 25.57; H, 1.29;
P, 5.93. Found for 3: C, 25.63; H, 1.19; P, 5.56. Calcd for
C47H22O22Os6P4: C, 25.61; H, 1.00; P, 5.62.
Reaction of Cluster 1 with [Os3(CO)10(µ-H)2]. This reaction
was similar to that in (c). Cluster 1 (60 mg, 0.045 mmol) was treated
with [Os3(CO)10(µ-H)2] (39 mg, 0.045 mmol) in toluene (10 mL)
at 100 °C for 4 h. The cluster [{H2Os3(CO)8}{µ3-1,2,4-η4-
(PPh)4CH2}{Os3(CO)11}] (5; Rf ) 0.55, 36 mg, 38%) was obtained
after TLC using CH2Cl2/hexane (3/7) as eluent. Anal. Found for 5:
C, 25.16; H, 1.22; P, 5.31. Calcd for C44H24O19Os6P4: C, 24.88;
H, 1.13; P, 5.84.
Reaction of I with [Os3(CO)10(µ-H)2]. This reaction was similar
to that in (c) above, except that [Os3(CO)10(µ-H)2] was used instead
of [Os3(CO)11(NCMe)]. [Os3(CO)10(µ-H)2] (160 mg, 0.19 mmol)
was treated with I (42 mg, 0.09 mmol) in toluene (10 mL) at 100
°C for 4 h. The cluster [{H2Os3(CO)8}2{µ4-1,2,3,4-η4-(PPh)4CH2}]
(6; Rf ) 0.67, 54 mg, 28%) was obtained after TLC using CH2Cl2/
hexane (3/7) as eluent. Anal. Found for 6: C, 24.28; H, 1.58; P,
5.57. Calcd for C41H26O16Os6P4: C, 24.14; H, 1.28; P, 6.07.
X-ray Crystallographic Studies. All single crystals for X-ray
diffraction analysis were obtained by slow evaporation of a saturated
CH2Cl2/hexane solution at -20 °C for several days or by slow
diffusion of hexane into dichloromethane solution at -20 °C, unless
specially specified. Crystal data and details of the measurement
for clusters 1-6 were given in Table 1. Diffraction intensities were
collected at 293 K on a Siemens CCD SMART diffractometer using
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å) and
the ω-2θ scan technique. The structures were solved by direct
methods, and the refinement was by the full-matrix least-squares
method with all non-hydrogen atoms refined anisotropically. All
computations were carried out using a SHELXTL software pack-
age.11
Results and Discussion
(c) At 100 °C with Equimolar Amounts. The reaction condi-
tions were similar to those in (a). [Os3(CO)11(NCMe)] (189 mg,
0.20 mmol) reacted with I (92 mg, 0.20 mmol) in toluene (10 mL)
in a 100 °C oil bath for 4 h. The resulting clear red reaction solution
Reactions of 1,2,3,4-tetraphenyl-1,2,3,4-tetraphospholane
(I) with the activated triosmium cluster [Os3(CO)11(NCMe)]
(Scheme 1) yield the series of mono- and disubstituted cluster
derivatives 1-4. The reaction at room temperature in an
equimolar ratio affords the monosubstituted triosmium cluster
[Os3(CO)11{(PPh)4CH2}] (1) in 65% yield. In cluster 1, I
(7) Johnson, B. F. G.; Lewis, J. Inorg. Synth. 1972, 13, 93.
(8) Nicholls, J. N.; Vargas, M. D. Inorg. Synth. 1989, 26, 290.
(9) Kaesz, H. D. Inorg. Synth. 1990, 28, 238.
(10) Baudler, M.; Vesper, J.; Junkes, P.; Sandmann, H. Angew. Chem.,
Int. Ed. Engl. 1971, 10, 940.
(11) Sheldrick, G. M. SHELXTL; Siemens, Madison, WI, 1997.
3792 Inorganic Chemistry, Vol. 41, No. 14, 2002

1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane
Table 1. Summary of Crystallographic Data for Clusters 1-6
1y
1r
2
3y
3r
4
5
6
formula
C36H22O11-
Os3P4
C36H22O11-
Os3P4
C47H22O22-
C47H22O22-
Os6P4‚CH2Cl2
C47H22O22-
Os6P4‚
C35H22O10Os3P4‚ C44H24O19-
C41H26O16-
Os6P4‚
Os6P4‚CH2Cl2‚
1/2C6H14
2331.74
orthorhombic
Ibca
1/2CH2Cl2
Os6P4
1/2CH2Cl2
2246.19
1/2CH2Cl2
2099.38
fw
cryst syst
space group C2/c
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
1325.02
monoclinic
1325.02
triclinic
P1h
10.01370(10) 13.4535(2)
13.3073(2)
2288.65
orthorhombic
Pna21
29.6352(7)
16.3231(3)
12.3117(3)
1339.47
2121.52
monoclinic
P21/n
12.2713(2)
37.6220(6)
monoclinic
P21/c
monoclinic
P21/c
monoclinic
C2/c
23.0038(3)
22.1105(3)
22.3926(3)
15.835 30(10) 15.423(1)
84.2150(10)
19.9501(6)
11.4949(3)
12.1994(7)
22.5939(13) 13.5080(2)
24.787 20(10)
39.05110(10)
25.11790(1) 18.1456(5)
18.7303(11) 21.687 00(10)
101.47(2)
77.5610(10)
89.5250(10)
1996.59(4)
2
96.05(2)
96.0110(10)
94.7990(10) 118.32
7809.27(16)
8
13022.5(2)
8
5955.6(2)
4
11531.5(3)
8
4138.3(2)
4
5144.6(5)
4
5932.18(12)
8
λ, Å
0.7107
9.960
4912
0.7107
9.739
1228
0.7107
11.913
8504
0.7107
19.532
4152
0.7107
13.403
8136
0.7107
9.397
2484
0.7107
22.411
3824
0.7107
26.064
7560
µ (mm-1
F(000)
)
no. of rflns
collected
34 929
18 573
39 338
38 320
76 277
36 807
41 886
22 161
no. of indep 9847
rflns
9586
8347
12 789
28 896
10 387
14 914
7200
Rint
0.0431
0.0493
0.0530
0.1278
0.950
0.0609
0.0458
0.0854
1.101
0.0715
0.0494
0.0752
1.037
0.0593
0.0583
0.1105
1.052
0.1594
0.0670
0.1185
0.947
0.0553
0.0360
0.0697
0.923
0.0381
0.0501
0.1033
1.164
R1a
0.0229
0.0441
0.982
wR2b
S(F2)
T (K)
293(2)
293(2)
293(2)
293(2)
293(2)
293(2)
293(2)
293(2)
a R1 ) ∑(|Fo| - |Fc|)/∑|Fo|. b wR2 ) [∑w(|Fo| - |Fc|)2/∑w(Fo)2]1/2
.
shows a η1 coordination mode, using one of the outer
phosphorus atoms to act as a monodentate P-donor. When
crystallized in dichloromethane/hexane, 1 presents single
crystals of two conformational isomers with different colors
(1y as yellow and 1r as red blocks). When the above reaction
is performed with a 2.5:1 cluster to ligand ratio, I acts as a
bidentate donor to give two structurally isomeric linked bis-
trinuclear clusters, [{Os3(CO)11}2{µ-1,4-η2-(PPh)4CH2}] (2)
and [{Os3(CO)11}2{{µ-1,3-η2-(PPh)4CH2}] (3), with good
yields (21% and 38%, respectively). 2 and 3 exhibit µ-1,4-
η2 and µ-1,3-η2 coordination modes, respectively. Two
configurational isomers (yellow form 3y and red form 3r)
are isolated for 3 due to the different orientations of the
phenyl group on the uncoordinated outer phosphorus atom.
A pair of enantiomers is observed in the unit cell of 3r. When
the reaction with equimolar amounts of reactants is carried
out at 100 °C, the disubstituted 1,4-bridged cluster [Os3-
(CO)10{µ-1,4-η2-(PPh)4CH2}] (4) is afforded in 42% yield.
In cluster 4, I also shows the µ-1,4-η2 coordination mode as
seen in 2. When the reaction is performed with a 2.5:1 cluster
to ligand molar ratio at 100 °C, only 2 is obtained. Cluster
1 can undergo further reactions with metal clusters and is
the precursor for clusters 2-5. When 1 reacts with an
equimolar amount of [Os3(CO)11(NCMe)] at room temper-
ature, 2 and 3 are obtained in good yields (32% and 45%,
respectively). The conversion of 1 into 4 can be achieved in
74% yield through the pyrolysis of the toluene solution of 1
at 100 °C for 4 h. When 1 reacts with an equimolar amount
of [Os3(CO)10(µ-H)2] in toluene at 100 °C for 4 h, the 1,2,4-
linked bis-trinuclear cluster [{(µ-H)2Os3(CO)8}{µ3-1,2,4-η3-
(PPh)4CH2}{Os3(CO)11}] (5) is formed in 38% yield, wherein
ligand I acts as a tridentate ligand and shows the µ3-1,2,4-
η3 coordination mode. When I reacts with a 2-fold molar
amount of [Os3(CO)10(µ-H)2] at 100 °C for 4 h, the 1,2,3,4-
linked bis-trinuclear hydride cluster [{(µ-H)2Os3(CO)8}2{µ4-
1,2,3,4-η4-(PPh)4CH2}] (6) is obtained in 28% yield, wherein
I presents the µ4-1,2,3,4-η4 coordination mode and acts as a
tetradentate P donor.
The structures of all of the new clusters obtained have
been established by X-ray crystallography and further
1
characterized by IR, FAB mass, and H and 31P NMR
spectroscopy and elemental analysis (the spectroscopic data
are listed in Table 2). Proton-decoupled phosphorus-31
(31P{1H}) NMR spectroscopy is very useful in the elucidation
of the structures of the compounds obtained in this study,
since the 1JPP values from directly bonded phosphorus atoms
are relatively large (∼200 Hz), while the 2JPP and 3JPP values
are much smaller and, thus, are readily identifiable from the
spectra. For this reason, we have determined that the
phosphorus-phosphorus bonds from the ligand moiety in
all the clusters obtained remain intact because two of the
phosphorus atoms in every cluster have two relatively large
1JPP coupling constants.
Spectroscopic and Structural Characterization. The
Two Conformational Isomers of the Cluster [Os3(CO)11-
{(PPh)4CH2}] (1). The carbonyl stretching region of the IR
spectrum for cluster 1 (Table 2) is very similar to those of
previously reported monosubstituted triosmium cluster de-
rivatives Os3(CO)11(L) (L ) (PPh)5,1b (PEt)5,1f or C6H4-
(PPh)3 4), which suggests a structural similarity to those
species. The 31P{1H} NMR spectrum offers further cor-
roborative evidence to support this proposal. For the signals
of two of the phosphorus atoms, we were able to determine
1
two JPP coupling constants (∼300 Hz) for each, indicating
that the P4C ring framework of the ligand I remains intact
in cluster 1. Of these two signals, the one (at 2.3 ppm) with
a smaller 1JPP coupling constant value (272.9 Hz) is assigned
to the coordinated P(1), as the magnitude of the 1JPP coupling
Inorganic Chemistry, Vol. 41, No. 14, 2002 3793

Ang et al.
Scheme 1a
a All CO groups on Os atoms are omitted for clarity.
constant is normally reduced when the lone-pair electrons
of a tricoordinate phosphorus atom are removed by com-
plexation.12
phosphine, phosphite),1,4,5,14-20 where the geometry is ap-
proximately based on the D3h form of [Os3(CO)12] with one
of the equatorial carbonyls replaced by the ligand and all
the axial carbonyls nearly perpendicular to the triosmium
plane. The range of the Os-Os bond lengths in cluster 1y is
2.8869(2)-2.9102(2) Å. The small difference (about 0.023
Å) in the Os-Os separations in 1y demonstrates that the
cone angle of the ligand I is not large. The P4C ring of the
ligand moiety has an envelope conformation with P(2), P(3),
P(4), and C(1) almost coplanar with a deviation of 0.06 Å,
As previously observed for the monosubstituted cluster
[Os3(CO)11{P(p-C6H4F)3}],13 cluster 1 has two crystalline
forms, a yellow form (1y) and a red form (1r). Dissolution
of 1r in dichloromethane gives a yellow solution with
spectroscopic properties (IR and 1H and 31P NMR spectros-
copy) identical with those from the solution of 1y. When a
solution of 1y or 1r is recrystallized, both crystalline forms
are also obtained.
(14) Benfield, R. E.; Johnson, B. F. G.; Raithby, P. R.; Sheldrick, G. M.
Acta Crystallogr. 1978, B34, 666.
(15) Ehrenreich, W.; Herberhold, M.; Suss-Fink, G.; Klein, H.-P.; Thewalt,
U. J. Organomet. Chem. 1983, 248, 171.
(16) Suss-Fink, G.; Pellinghelli, M. A.; Tiripicchio, A. J. Organomet. Chem.
1987, 320, 101.
(17) Bruce, M. I.; Liddell, M. J.; Hughes, C. A.; Skelton, B. W.; White,
A. H. J. Organomet. Chem. 1988, 347, 157.
The structures of both the yellow form (1y) and the red
form (1r) of the cluster 1 have been determined by X-ray
diffraction analysis. The molecular structures of 1y and 1r
are shown in Figure 1 together with the atomic labeling
schemes. Selected bond lengths and angles are given in Table
3. The structure of 1y has the typical structure for the
monosubstituted triosmium cluster [Os3(CO)11(PR3)] (PR3 )
(18) Heuer, L.; Schomburg, D. J. Organomet. Chem. 1995, 495, 53.
(19) Johnson, B. F. G.; Lewis, J.; Nordlander, E.; Raithby, P. R. J. Chem.
Soc., Dalton Trans. 1996, 3825.
(12) Jameson, C. J. In Phosphorus-31 NMR Spectroscopy in Stereochemical
Analysis: Theoretical Considerations: Spin-Spin Coupling; Verkade,
J. G., Quinn, L. D., Eds.; VCH: New York, 1987; Chapter.6.
(13) Hansen, V. M.; Ma, A. K.; Biradha, K.; Pomeroy, R. K.; Zaworotko,
M. J. Organometallics 1998, 17, 5267.
(20) (a) Ang, H. G.; Kwik, W. L.; Leong, W. K.; Potenza, J. A. Acta
Crystallogr. 1989, C45, 1713. (b) Ang, H. G.; Cai, Y. M.; Kwik, W.
L.; Leong, W. K.; Tocher, D. A. Polyhedron 1991, 10, 881. (c) Ang,
H. G.; Cai, Y. M.; Kwik, W. L. J. Organomet. Chem. 1993, 448,
219.
3794 Inorganic Chemistry, Vol. 41, No. 14, 2002

1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane
Table 2. Spectroscopic Data for Clusters 1-6
complex
IR ν(CO),a cm-1
1H NMR, δ (J, Hz)b
31P{1H} NMR, δ (J, Hz)b
MS, m/zc
1
2105 m, 2052 s,
2035 m, 2018 vs,
1999 w, 1986 m,
1970 w
2107 m, 2057 s,
2035 w, 2023 vs,
1990 w, 1968 w
6.9-7.7 (m, 20H, Ph)
3.9 (m, 1H, CH2)
3.2 (m, 1H, CH2)
20.0 (ddd, 288.1, 19.1, 5.0, P4)
5.9 (ddd, 307.3, 288.1, 8.1, P3)
2.3 (ddd, 272.9, 19.2, 8.1, P1)
-2.2 (ddd, 307.3, 272.9, 5.0, P2)
AA′XX′ spin pattern
1325
(1325)
2
7.1-7.6 (m, 20H, Ph)
3.8 (m, 2H, CH2)
2204
(2204)
δA -19.4, δX -28.1
JXX′ ) 6.7, JAA′ ) 192.2
JAX ) 262.7, JAX′ ) 14.0
3r
3y
4
2106 m, 2057 s,
2036 w, 2023 vs,
1989 w, 1968 w
6.7-8.0 (m, 20H, Ph)
3.7 (m, 1H, CH2)
3.2 (m, 1H, CH2)
14.6 (ddd, 305.0, 15.8, 5.5, 1P)
5.8 (m, 1P)
2204
(2204)
3.8 (m, 1P)
-7.8 (305.0, 269.2, 61.6, 1P))
4.2 (ddd, 339.4, 79.0, 4.5, P1 or P4)
-0.5 (ddd, 290.2, 275.8, 4.5, P2 or P3)
-20.2 (ddd, 275.8, 79.0, 20.3, P1 or P4)
-27.6 (ddd, 339.4, 290.2, 20.3, P2 or P3)
8.9 (ddd, 232.7, 206.0, 18.0, P2 or P3)
-20.3 (dd, 293.8, 232.7, P2 or P3)
-28.8 (ddd, 293.7, 72.5, 18.0, P1 or P4)
-34.3 (206.0, 72.5, P1 or P4)
32.0 (ddd, 201.8, 143.5, 73.4, P2)
4.6 (ddd, 169.9, 73.4, 20.1, P4)
-4.2 (ddd, 201.8, 169.9, 58.5, P3)
-12.2 (ddd, 143.5, 58.5, 20.1, P1)
2106 m, 2057 s,
2036 w, 2023 vs,
1989 w, 1968 w
6.7-8.0 (m, 20H, Ph)
3.7 (m, 1H, CH2)
3.2 (m, 1H, CH2)
2204
(2204)
2094 s, 2035 w,
2017 s, 2008 vs,
1976 w
6.7-8.2 (m, 20H, Ph)
3.6 (m, 2H, CH2)
1297
(1297)
5
2110 m, 2074 m,
2059 m, 2022 vs,
2007 s, 1995 s,
1951 w
6.7-8.3 (m, 20H, Ph)
4.1 (m, 1H, CH2)
3.6 (m, 1H, CH2)
-10.5 (m, 1H, M-H)
-10.8 (m, 1H, M-H)
7.2-8.0 (m, 20H, Ph)
3.9 (m, 2H, CH2)
2121
(2121)
6
2083 w, 2069 s,
2049 w, 2013 vs,
1995 w, 1956 w
AA′BB′ spin pattern
δA 17.0, δB -1.1
JAA′ ) 206.5, JXX′ ) 0;
JAX ) 145.7, JAX′ ) 28.8
2040
(2040)
-10.6 (d, 2H, M-H)
-11.0 (d, 2H, M-H)
1
a In CH2Cl2. b In CDCl3 with SiMe4 for H and 85% H3PO4 for 31P as references. c Simulated values given in parentheses.
Figure 1. ORTEP drawings (thermal ellipsoid 30% probability) of clusters 1y and 1r.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for Clusters 1
The most significant difference in the structures of 1r and
1y is the orientation of the axial carbonyls. In 1r, the
pseudoaxial carbonyls are severely twisted with respect to
each other. The extent of this twisting is measured by the
absolute value of the dihedral angle between the averaged
planes Cax-Os(2)-Cax-Os(3) and Cax-Os(3)-Cax-Os(2)
of the Os2(CO)8 fragment of the clusters. In 1r this dihedral
angle (i.e., that between the C(23)Os(2)C(24)Os(3) and
C(34)Os(3)C(33)Os(2) planes) is 27.7°. The corresponding
angle for 1y is 13.0°. The Os-Os distances in 1r (ranging
from 2.8672(5) to 2.9090(5) Å) are shortened compared to
the corresponding distances in 1y. These shorter bond lengths
suggest that the metal-metal bonds in 1r are somewhat
stronger than those in 1y, which is in contrast to the
observation for the yellow and red forms of [Os3(CO)11{P(p-
C6H4F)3}]13 and contrary to the view that in the staggered
form of M3(CO)12 there is less metal-metal bonding than
in the eclipsed form.22
and 4
1y
1r
4
Os(1)-Os(2)
2.8928(2)
2.8869(2)
2.9102(2)
2.3472(9)
2.8672(5)
2.8724(5)
2.9090(5)
2.342(2)
2.8934(8)
2.8794(9)
2.8888(8)
2.343(4)/
2.344(4)
Os(2)-Os(3)
Os(3)-Os(1)
Os(1)-P(1)/
Os(3)-P(4)
P-P (range)
2.205(2)-
2.239(2)
2.198(3)-
2.217(3)
2.223(5)-
2.276(6)
Os-Os-Os
(range)
P-Os-Os
(range)
59.665(5)-
60.467(5)
100.66(2)
59.46(2)-
60.91(2)
106.17(5)
59.73(2)-
60.21(2)
87.4(1)-
91.80(9)
and the coordinated phosphorus atom P(1) is out of the above
plane at a distance of 0.12 Å. The phenyl groups attached
to the neighboring phosphorus atoms adopt an all-trans
configuration, which is similar to that in the free ligand.21
(21) Lex, V. J.; Baudler, M. Z. Anorg. Allg. Chem. 1977, 431, 49.
Inorganic Chemistry, Vol. 41, No. 14, 2002 3795

Ang et al.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for Clusters 2, 3, 5, and 6
2a
3y
2.8775(4) 2.8630(8)
3rb
5
6c
Os(1)-Os(2)
Os(2)-Os(3)
Os(3)-Os(1)
Os(4)-Os(5)
Os(5)-Os(6)
Os(6)-Os(4)
Os-P (range)
P-P (range)
2.8778(6), 2.8818(6)
2.8738(7), 2.8624(6)
2.9098(7), 2.8814(7)
2.8707(7), 2.8663(7)
2.8610(7), 2.8642(6)
2.9186(7), 2.9116(7)
2.327(3)-2.367(3)
2.199(4)-2.279(4)
2.8645(4)
2.8710(4)
2.8887(4)
2.6696(3)
2.7883(4)
2.8130(4)
2.337(2)-2.339(2)
2.230(2)-2.289(2)
2.6823(6)
2.8168(6)
2.7992(6)
2.8941(5)
2.9182(4)
2.8755(9)
2.9062(8)
2.8741(8)
2.8777(8)
2.9103(8)
2.341(2)
2.212(4)-2.232(3)
2.345(3)-2.351(4)
2.226(5)-2.250(5)
2.315(2)-2.332(3)
2.261(5)-2.263(4)
Os-Os-Os (range)
P-P-P (range)
P-Os-Os (range)
59.35(2)-60.74(2)
90.22(9)
108.77(6)
59.36(2)-60.85(2)
94.1(2) - 98.2(2)
100.5(1)-101.55(9)
59.23(2)-61.22(2)
97.9(2)-102.6(2)
98.65(7)-111.19(7)
56.926(8)-62.00(2)
86.51(8)-91.05(8)
94.67(4)-111.38(4)
57.06(2)-61.80(2)
86.9(2)
94.65(6)-95.74(6)
a A 2-fold axis passes through C(1) and the midpoint of P(2)-P(2A); the two parts of the molecule are equal. b Two molecules exist in the unit cell. c A
2-fold axis passes through C(1) and the midpoint of P(1)-P(1A); the two parts of the molecule are equal.
The origin of the staggered configuration of the red isomer
of 1 may be the same as that for the cluster Os3(CO)11[P(p-
C6H4F)3].13 As discussed before, the cone angle of ligand I
is not large; hence, unlike the case for the ligand P(But)3,13
which has a large cone angle, steric effects cannot be the
cause of this twisting. In comparison with the other cyclo-
polyphosphines, which we have previously studied, I has
no extraordinary σ-donor or π-acceptor properties; therefore,
the twisting of 1r looks unlikely to be due to any unusual
1
electronic properties of I. Spectroscopic results (IR and H
and 31P NMR spectra) show that both 1y and 1r have
identical properties in the solution state. This suggests that
intermolecular interactions in the solid state may cause the
twisting in 1r.
Figure 2. ORTEP drawing (thermal ellipsoid 30% probability) of cluster
2.
Structural Isomers [{Os3(CO)11}2{µ-1,4-η2-(PPh)4CH2}]
neighboring Ph1. This results in a severely distorted P4C ring
framework with P(1) and P(1A) symmetrically located on
opposite sides of the plane C(1)P(2)P(2A) at a distance of
(2) and [{Os3(CO)11}2{µ-1,3-η2-(PPh)4CH2}] (3). The IR
spectra of clusters 2 and 3 are very similar to those of
previously reported linked bis-trinuclear clusters [{(Os3-
0.378 Å. Unlike the 1,3-linked cluster 3 discussed below,
(CO)11}2{µ-η2-(L)}].1b,4,5,23 As in the free ligand,24 the
the 1,4-linked cluster 2 has low solubility in most common
solvents, which may be due to its higher symmetry.
31P{1H} NMR spectrum of cluster 2 shows a typical AA′XX′
second-order spin pattern, from which we can calculate JAA′
When pure cluster 3 is crystallized in CH2Cl2/hexane (1:
4), crystals of two colors (red, 3r; yellow, 3y) are obtained.
The 31P{1H} NMR spectrum of a freshly prepared solution
of 3r in CDCl3 shows two sets of signals with four
phosphorus resonances each. The integration intensity ratio
of the two sets is 2.4:1. When the spectrum of 3y is recorded
under the same conditions, the same pattern of signals is
obtained but with different relative intensities (1.1:1). This
demonstrates that the pure compound 3r in the solid state
can partly convert to 3y in the solution state and vice versa.
The conversion rate is slow compared to the NMR time scale
even at elevated temperature (80 °C) in d8-toluene solution.
At room temperature, a solution of 3r in CDCl3 takes 32 h
to establish the equilibrium with a final intensity ratio of
1.6:1, while 3y requires 26 h to reach equilibrium with the
same intensity ratio. It is reasonable to assign the set of
signals with greater intensities to 3r and the other to 3y. In
3y, the P(1) and P(4) atoms have an unusually large coupling
(2JPP ) 79.0 Hz), which may be attributed to their proximity
(the nonbonding distance between the two atoms is 3.07 Å).
The structures of both 3r and 3y have been determined
by X-ray diffraction and are shown in Figure 3, together with
the atomic numbering scheme. Selected important bond
) 192.2 Hz. JXX′ ) 6.7 Hz, JAX ) 262.7 Hz, and JAX′
)
14.0 Hz.25 Of the two possible modes of coordination (i.e.
two triosmium triangles coordinating with either the two
outer phosphorus atoms or the two central phosphorus atoms)
X-ray crystallographic results confirm the coordination via
the outer phosphorus atoms.
The molecular structure of 2 is depicted in Figure 2
together with the atomic labeling scheme, and selected
structural parameters are listed in Table 4. A crystallographic
2-fold axis passes through C(1) and the midpoint of the
P(2)-P(2A) bond relating the two equal halves of the
molecule. In the molecule, ligand I links two different
triosmium triangles via the equatorial positions using two
symmetrical outer phosphorus atoms P(1) and P(1A) and
adopting a µ-1,4-η2 coordination mode. Unlike the all-trans
configuration in the free ligand, in the ligand moiety of
cluster 2, Ph2 adopts a cis configuration with respect to
(22) Lauher, J. W. J. Am. Chem. Soc. 1986, 108, 1521.
(23) Amoroso, A. J.; Johnson, B. F. G.; Lewis, J.; Massey, A. D.; Raithby,
P. R.; Wong, W. T. J. Organomet. Chem. 1992, 440, 219.
(24) Hoffman, P. R.; Caulton, K. G. Inorg. Chem. 1975, 14, 1997.
(25) Sohar, P. In Nuclear Magnetic Resonance Spectroscopy; CRC Press:
Boca Raton, FL, 1983; Vol. 1, Chapter 1.
3796 Inorganic Chemistry, Vol. 41, No. 14, 2002

1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane
Figure 3. ORTEP drawings (thermal ellipsoid 30% probability) of clusters 3y and 3r.
Chart 1. Schematic Structure of Cluster 3
The P4C ring of the ligand in 3r has an envelope
configuration, with C(1), P(2), P(3), and P(4) almost coplanar
(with a deviation of 0.04 Å) and P(1) out of the plane at a
distance of 0.15 Å. The conformations of the axial carbonyl
groups of the two discrete triosmium triangles in 3r are
different. In the Os(1)-Os(2)-Os(3) triangle, the axial
carbonyl groups give an eclipsed configuration with a
dihedral angle of 4.2° between C(24)Os(2)Os(3)C(21) and
C(34)Os(3)Os(2)C(33), while in the Os(4)Os(5)Os(6) tri-
angle, the pseudoaxial carbonyl groups are severely twisted.
The dihedral angle between C(64)Os(6)Os(5)C(61) and
C(53)Os(5)Os(6)C(51) is 23.6°.
The two coordinated phosphorus atoms in cluster 3 are
both chiral atoms; thus, theoretically as many as four
diastereomers could be present in both 3y and 3r. For the
free ligand in the solution state, the phenyl groups on the
phosphorus atoms in the P4C ring adopt an all-trans config-
uration, which has been confirmed by NMR spectroscopy;24
thus, the free ligand has a pair of enantiomers in the solution
state. As shown in Scheme 2, the enantiomeric pair in ligand
I gives rise to a pair of enantiomers of the monosubstituted
cluster 1, which is confirmed by the X-ray structure. It
follows then that the enantiomeric pair of cluster 1 gives
rise to a pair of enantiomers in 3r. Similarly, there should
also be a pair of enantiomers in 3y.
The Cluster [Os3(CO)10{µ-1,4-η2-(PPh)4CH2}] (4). The
IR spectrum (carbonyl stretching region) of cluster 4 shows
a vibrational pattern similar to that for previously reported
bridged trinuclear clusters [Os3(CO)10{µ2-η2-(L)].1b,4,5,26-28
The NMR spectra clearly indicate that the P4C ring frame-
parameters for both molecules are listed in Table 4. Clusters
3 and 2 are structural isomers. Unlike the case in the free
ligand, the phenyl group on the uncoordinated outer phos-
phorus atom (Ph4) has a cis configuration with respect to
the neighboring Ph3, which results in a twisted configuration
of the P4C ring with C(1) and P(4) on opposite sides of the
plane P(1)P(2)P(3) at distances of 0.09 and 0.31 Å, respec-
tively.
There are two independent molecules, which are a pair of
enantiomers, in the unit cell of 3r. At the same time, clusters
3r and 3y are convertible configurational isomers. The
structures of 3r and 3y differ essentially in the orientations
of the Ph4 group (Chart 1). Unlike 3y and just like the free
ligand, Ph4 in 3r has a trans configuration with respect to
the neighboring phenyl (Ph3). Obviously, the steric crowding
among phenyl groups is more pronounced in isomer 3y than
that in 3r, as shown by the distortion of the P4C rings. In 3y
this overcrowding is partly or totally compensated by the
lesser repulsion between Ph4 and the Os(CO)3 unit, with the
Ph4 group pointing away from the Os(CO)3 unit. This kind
of isomeric relationship has been previously reported.1c,5
(26) Clucas, J. A.; Dawson, R. H.; Dolby, P. A.; Harding, M. M.; Pearson,
K.; Smith, A. K. J. Organomet. Chem. 1986, 311, 153.
(27) Deeming, A. J.; Donovan-Mtunzi, S.; Hardcastle, K. I.; Kabir, S. E.;
Henrick, K.; McPartlin, M. J. Chem. Soc., Dalton Trans. 1988, 579.
Inorganic Chemistry, Vol. 41, No. 14, 2002 3797

Ang et al.
Scheme 2
Figure 4. ORTEP drawing (thermal ellipsoid 30% probability) of cluster
4.
work of ligand I remains intact in the cluster. The molecular
structure of cluster 4 is given in Figure 4 together with the
atomic labeling scheme, and the important bond lengths and
angles are listed in Table 3. In the cluster, ligand I acts as a
bidentate donor, occupying equatorial sites on the osmium
triangle plane and bridging over an Os-Os edge through
the two outer phosphorus atoms P(1) and P(4), adopting a
µ-1,4-η2 coordination mode. Unlike the monosubstituted
triosmium cluster derivatives, the three Os-Os edges are
not very different in length (ranging from 2.8794(9) to
2.8934(8) Å). The bridged edge Os(1)-Os(3) is not the
longest Os-Os separation, which is in contrast to the
observations in previously reported bridged triosmium
clusters [Os3(CO)10{µ-η2-L}] (where L ) PhP(CH2)nPPh, n
) 2-4).27,28 The P4C ring of the ligand has a twisted
configuration with P(1) and C(1) atoms nearly symmetrically
located on opposite sides of the P(2)P(3)P(4) plane at
distances of 0.133 and 0.170 Å, respectively. Unlike the free
ligand, Ph4 adopts a cis configuration with respect to the
neighboring Ph3. To accommodate the relatively short Os-
Os edge distance, the angle P(1)-C(5)-P(4) (102.1(6)°) is
significantly smaller than that in the free ligand (116.62(77)°).21
Among the nonbonding P‚‚‚P distances, P(1)‚‚‚P(4) is
exceptionally short (2.895 Å), while the other two distances
are 3.294 and 3.426 Å, respectively. This short distance can
Figure 5. ORTEP drawing (thermal ellipsoid 30% probability) of cluster
5.
clearly indicates the existence of two metal hydrides (δ at
-10.4 and -10.8 ppm, respectively) in the cluster.
Suitable red single crystals of 5 for X-ray crystallography
are obtained via the slow evaporation of a saturated
chloroform solution at ambient temperature. The molecular
structure is given in Figure 5 together with the atomic
labeling scheme, and selected bond parameters are listed in
Table 4. The cluster 5 can be considered as an extension of
the monosubstituted cluster 1 with the two other phosphorus
atoms (P(2) and P(4)) in the ligand moiety coordinating with
another triosmium triangle via the displacement of two
carbonyl groups of the parent [Os3(CO)10(µ-H)2]. Ligand I
in cluster 5 adopts the µ3-1,2,4-η3 coordination mode. Like
the parent cluster [Os3(CO)10(µ-H)2],29 one of the Os-Os
distances (i.e. Os(4)-Os(5) ) 2.6696(3) Å) is unusually short
compared with the normal Os-Os single bond. We can
tentatively assign the two spectroscopically detected hydrides
to be bridging across the unusually short edge Os(4)-Os(5)
2
explain why JP(1)-P(4) is extraordinarily large (72.5 Hz).
The Cluster [Os3(CO)11{µ3-1,2,4-η3-(PPh)4CH2}Os3-
(CO)8(µ-H)2] (5). The 31P{1H} NMR spectrum of 5 shows
an almost perfect first-order pattern with four resonance
1
signals of equal intensity. All the JPP coupling constants
are unusually small, possibly due to the high degree of
complexation of the trivalent phosphorus atoms. We assign
1
the smallest JPP value (143.5 Hz) to the coupling between
the two coordinated phosphorus atoms P(1) and P(2) with
1
the aid of the X-ray structure. The H NMR spectrum also
(29) (a) Churchill, M. R.; Hollander, F. J.; Hutchinson, J. P. Inorg. Chem.
1977, 16, 2697. (b) Broach, R. W.; Williams, J. M. Inorg. Chem. 1979,
18, 314.
(28) Kabir, S. E.; Miah, A.; Nesa, L.; Uddin, K.; Hardcastle, K. L.;
Rosenberg, E.; Deeming, A. J. J. Organomet. Chem. 1986, 311, 153.
3798 Inorganic Chemistry, Vol. 41, No. 14, 2002

1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane
Scheme 3
that in the free ligand (2.205 Å) because of the coordination
with heavy metal atoms.
Figure 6. ORTEP drawing (thermal ellipsoid 30% probability) of cluster
6.
Reactivity of the Monosubstituted Cluster [Os3(CO)11-
{(PPh)4CH2}] (1). Our experimental results demonstrate that
the other three noncoordinated phosphorus atoms in cluster
1 can also participate in the coordination with metal atoms
(Scheme 3). When cluster 1 reacts with an equimolar amount
of the activated triosmium cluster [Os3(CO)11(NCMe)] at
room temperature overnight, P(3) or P(4) can further
coordinate to another cluster molecule and the 1,3- and 1,4-
linked bis-trinuclear clusters 2 and 3 are obtained in 32%
and 45% yields, respectively. When the solution of 1 in
toluene is pyrolyzed at 100 °C for 4 h, the carbonyl groups
in 1 are labilized and are displaced by the uncoordinated
P(4) atom to give the disubstituted 1,4-bridged cluster 4.
When cluster 1 reacts with an equimolar amount of
[Os3(CO)10(µ-H)2] at 100 °C for 4 h in toluene, further
coordination via P(2) and P(4) to another cluster molecule
takes place to give the 1,2,4-linked bis-trinuclear cluster
[Os3(CO)11{µ3-1,2,4-η3-(PPh)4CH2}{Os3(CO)8(µ-H)2}] (5).
(giving rise to some metal-metal double-bond character) on
the basis of the electron count of 46 for the Os(4)Os(5)-
Os(6) triosmium unit. The phenyl groups on the phosphorus
atoms of the ligand moiety adopt an all-trans configuration.
The P4C ring of the ligand has the envelope configuration
with C(1), P(1), P(3), and P(4) atoms almost coplanar
(maximum deviation 0.022 Å), while P(2) is out of the above
plane at a distance of 0.496 Å. The P(1)-P(2) distance
(2.289(2) Å) is apparently longer than the other P-P bonds
(average 2.232(2) Å) and than that in the free ligand (average
2.205 Å), which may be due to the coordination of both
phosphorus atoms with heavy metals. The P(2)‚‚‚P(4)
distance (3.060 Å) is shortest among the nonbonding
phosphorus-phosphorus distances; thus, we have assigned
the large 2JPP coupling constant (73.4 Hz) to be between these
two phosphorus atoms. The P-Os bond distances are located
in the typical range for such bonds.
The Cluster [{Os3(CO)8(µ-H)2}2{µ4-1,2,3,4-η4-(PPh)4-
CH2}] (6). As also observed for cluster 2, the 31P{1H} NMR
spectrum of cluster 6 shows an AA′XX′ spin pattern. The
1H NMR spectrum shows the existence of two sets of metal
hydrides in the cluster with chemical shifts at -10.6 and
-11.0 ppm, respectively.
Conclusions
Reactions of 1,2,3,4-tetraphenyl-1,2,3,4-tetraphospholane
(I) with the activated triosmium cluster [Os3(CO)11(NCMe)]
or [Os3(CO)10(µ-H)2] under various conditions afford a series
of trinuclear and linked bis-trinuclear clusters via the
substitution of labile acetonitrile or carbonyl groups in parent
clusters, wherein the ligand I shows a variety of coordination
modes (η1, µ-1,3-η2, µ-1,4-η2, µ3-1,2,4-η3, µ4-1,2,3,4-η4).
Because of the coordination with metal atoms, the P-P
bond(s) in the ligand moiety comprising the coordinated
phosphorus are elongated compared with those of the free
ligand. In cases where there are two M-P linkages, the extent
of elongation of this bond is found to be even more
pronounced. The magnitude of the 1JPP coupling constant is
observed to be smaller, and again the extent of reduction is
more significant when there are two M-P linkages. The
existence of the red staggered conformer 1r and the yellow
eclipsed conformer 1y in cluster 1 may stem from the
intermolecular interactions in the crystalline state, while the
two convertible configurational isomers (3y and 3r) in the
1,3-linked bis-trinuclear cluster 3 arise due to the competition
of the repulsion effect between the Ph4 on the uncoordinated
The molecular structure of cluster 6 is given in Figure 6
together with the atomic labeling scheme, and the selected
bond parameters are listed in Table 4. A crystallographic
2-fold axis passes through C(1) and the midpoint of the
P(1)-P(1A) bond, resulting in the identical halves of the
molecule. In the molecule, ligand I links each of the two
different Os3(CO)8(µ-H)2 units via one outer and one central
phosphorus atom with the substitution of the carbonyl groups
to adopt the µ4-1,2,3,4-η4 coordination mode. Like cluster
5, the Os(1)-Os(2) bond (2.6823(6) Å) has the properties
of a double bond with two bridging hydrides, one above and
the other below the osmium triangle plane. As in the free
ligand, the phosphorus atoms in cluster 6 adopt the all-trans
configuration. The P4C ring has a twisted configuration with
P(1) and P(1A) located symmetrically on opposite sides of
the P(2)C(1)P(2A) plane at a distance of 0.13 Å. The average
P-P bond length (2.262 (2) Å) is elongated compared with
Inorganic Chemistry, Vol. 41, No. 14, 2002 3799

Ang et al.
P(4) and the Os(CO)4 unit with the repulsion among the
phenyl groups attached on the intercyclic phosphorus atoms.
The ligand I is chiral at all coordinated phosphorus atoms,
which results in the range of isomers obtained for some of
the products. The high versatility of coordination modes in
I may arise from the smaller cone angle of the two outer
phosphorus atoms compared with other cyclopolyphos-
phines and the ready folding modes in the P4C five-
membered-ring, which preserves the ligand ring integrity
after complexion.
Acknowledgment. We thank the National University of
Singapore for financial support and for a Research Scholar-
ship (to X.Z.).
Supporting Information Available: Complete listings of
atomic positions, bond lengths and angles, anisotropic thermal pa-
rameters, hydrogen coordinates, data collection, and crystal param-
eters for all crystallographically characterized complexes. This ma-
terial is available free of charge via the Internet at http://pubs.acs.org.
IC025589C
3800 Inorganic Chemistry, Vol. 41, No. 14, 2002