the ring and holds the three osmium atoms together by bonding
to each of them, while the other two phosphorus atoms bridge
the two open edges of the osmium triangle. The bond length of
P(2)–Os(1) [2.4424(12) Å] is slightly longer than that of P(2)–
Os(2) [2.3690(13) Å] and P(2)–Os(3) [2.3610(13) Å]. That
means the distances between the capping phosphorus atom and
the two bonded osmium atoms are shorter than those between
the capping phosphorus atom and the non-bonded osmium
atoms.
in 4. 2 and 4 are isomers, differing in the orientation of the
phenyl group attached to the central unco-ordinated phos-
phorus atom of the ligand ring: in 2 it bends away from the
osmium triangle while in 4 it points towards the osmium
triangle.
Unlike clusters 1, 2, 3 and 4, which are structurally similar to
those obtained with the five-membered homo-cyclopoly-
phosphine (PPh)5, clusters 5 and 6, derived from cleavage of
P–P bond(s), are structurally different. Transformation of
clusters 1, 2 and 4 to 5 and then to 6 is a result of progressive
cleavage of the P–P bonds and the Os–Os bonds leading
finally to the incorporation of ‘Os(CO)3’ and ‘PhP’ units in the
structural framework of 6.
The 31P-{1H} NMR spectrum of cluster 5 shows three sets of
signals: δ Ϫ95.4 (dd, J1 = 42.0, J2 = 6.6), 57.2 (dd, J1 = 232.7,
J2 = 6.9) and 0.09 (dd, J1 = 232.4, J2 = 41.8 Hz). From the coup-
ling constant values we can deduce that one P–P bond in the
cyclic ligand has been cleaved, i.e. the PhPCPh᎐CPhPPhPPh
᎐
fragment exists. It is easy to assign the signal at δ Ϫ95.4 (dd) to
P(3), the atom which bridges the non-bonded Os ؒ ؒ ؒ Os edge. It
is rather difficult to assign the other peaks to either P(1) or P(2).
The 31P-{1H} NMR spectrum of 6 shows two sets of signals at
δ Ϫ154.8 (d, 2P) and Ϫ242.3 (t, 1P). The first is assigned to the
two phosphorus atoms that bridge the two non-bonded
osmium atoms, while the second is assigned to the phosphorus
atom that caps the three osmium atoms.
Experimental
General comments
The reactions were carried out in evacuated reaction tubes
using vacuum-line techniques. All solvents were dried using
appropriate drying agents and distilled prior to use. The com-
pounds PhPPhPPhPCPh᎐CPh,2 [Os3(CO)11(MeCN)]15,16 and
᎐
[Os3(CO)10(MeCN)2]17 were prepared by literature methods.
The products of the reactions were separated by thin-layer
chromatography on 20 × 20 cm glass plates coated with 0.3 mm
of Merck Kieselgel 60 GF254 using mixtures of dichloro-
methane and hexane in various proportions as eluents. Infrared
spectra were recorded as solutions in 0.5 mm KBr cells on a
Conversion of cluster derivatives
The conversion of cluster derivatives is summarized in Scheme
2. Heating 1 at 80 ЊC overnight enables the complete conversion
Bio-Rad FTS 160 FT-IR spectrophotometer, and H and 31P
1
NMR spectra on a Bruker ACF-300 NMR MHz spectrometer
using SiMe4(1H) and H3PO4(31P) as references. Fast Atom
Bombardment (FAB) mass spectra were obtained on a Finnigan
MAT 95 XL(T) mass spectrometer.
Reaction of PhPPhPPhPCPh᎐CPh with [Os (CO) (MeCN)]
᎐
3
11
(a) At room temperature. The ligand L (60 mg, 0.120 mmol)
was added to a solution of [Os3(CO)11(MeCN)] (111 mg, 0.120
mmol) in dichloromethane (10 ml). The mixture was stirred at
room temperature overnight during which time it changed from
yellow to orange. The solvent was removed under vacuum and
TLC of the residue using dichloromethane–hexane (1:4) as
eluent afforded compounds 1 (Rf = 0.23, 32.6 mg, 19.7%)
(Found: C, 36.95; H, 2.03; P, 6.43. C43H25O11Os3P3 requires: C,
37.39; H, 1.82; P, 6.72%) and 2 (Rf = 0.13, 8 mg, 4.9%) (Found:
C, 37.08; H, 2.29; P, 6.19. C42H25O10Os3P3 requires: C, 37.28; H,
1.86; P, 6.87%).
The ligand L (63 mg, 0.124 mmol) reacted with [Os3(CO)11-
(MeCN)] (228 mg, 0.248 mmol) under similar conditions to
afford compounds 1 (59.7 mg, 34.8%), 2 (15 mg, 8.9%) and 3
(Rf = 0.13, 8 mg, 2.8%) (Found: C, 28.72; H, 1.35; P, 3.78.
C54H25O22Os6P3 requires: C, 28.70; H, 1.11; P, 4.11%).
(b) At 80 ЊC. [Os3(CO)11(MeCN)] (112 mg, 0.122 mmol), lig-
and L (61.2 mg, 0.122 mmol) and dichloromethane (10 ml) were
mixed in a Carius tube. After the mixture was degassed, the
Carius tube was sealed in vacuum, placed in an iron pipe,
and heated in an oven at 80 ЊC for 17 h. The solution turned
from yellow to orange. Excess of solvent was removed under
vacuum. TLC of the residue using dichloromethane–hexane
(1:4) as eluent afforded compounds 2 (24.1 mg, 14.6%) and 5
(Rf = 0.38, 39.5 mg, 13.64%) (Found: C, 37.34; H, 2.07; P, 6.49.
C41H25O9Os3P3 requires: C, 37.16; H, 1.90; P, 7.01%) and 6
(Rf = 0.47, 5 mg, 3.1%) (Found: C, 36.93; H, 2.12; P, 6.63.
C41H25O9Os3P3 requires: C, 37.16; H, 1.90; P, 7.01%).
Scheme 2 Conversion of the cluster derivatives.
into 5, while 2 and 4 can also be partially converted into 5.
Complete conversion from 5 to 6 can be achieved by heating 5
at 140 ЊC overnight. Heating 3 at 80 ЊC resulted in the form-
ation of 2, 5 and [Os3(CO)12]. The reaction pathways involve the
cleavage of P–P bond(s), attack of the phosphorus lone pair(s)
on the osmium atoms, and cleavage of an Os–Os bond.
Conclusion
The
reactions
of
the
five-membered
heterocyclic
PhPPhPPhPCPh᎐CPh with [Os (CO)12 Ϫ n(NCMe)n] (n = 1 or
᎐
3
Reaction of PhPPhPPhPCPh᎐CPh with [Os (CO) (MeCN) ]
᎐
3
10
2
2) under different conditions afford a series of new clusters 1–6.
In 1, 2, 3 and 4 the ligands are all intact with different configur-
ations with respect to the phenyl groups attached to the three P
atoms: trans, cis in 1, cis, cis in 2, trans, trans in 3 and trans, trans
(a) At room temperature. The ligand L (88 mg, 0.176 mmol)
was added to a solution of [Os3(CO)10(MeCN)2] (164 mg, 0.176
mmol) in dichloromethane (10 ml). The mixture was stirred at
J. Chem. Soc., Dalton Trans., 2000, 3429–3434
3433
Ang, How Ghee
