Ortho phosphorylation of PPh3 to give a diphosphine and formation of a butterfly structure on a tetrairidium framework

Article abstract of DOI:10.1021/om049303i

A brief thermolysis of the bis-phosphine-substituted tetrairidium cluster Ir₄(CO)₁₀(PPh₃)₂ (1) in chlorobenzene (CB) converts it rapidly to the diphosphine cluster Ir ₄(CO)₇(μ-CO)₃{κ²-Ph ₂P(o-C₆H₄)PPh₂} (2) in 53% yield, providing evidence for ortho phosphorylation at the tetrairidium cluster framework. Treatment of 2 with excess C₆₀ affords the butterfly Ir₄-C₆₀ complex Ir ₄(CO)₆)(μ-CO){μ₃-κ²- Ph₂P(o-C₆H₄)P(η¹-o-C ₆H₄)}(μ₃-η²: η²η²-c₆₀ (3) in 71% yield. Interestingly, compound 3 can be prepared directly from the thermolysis of 1 with excess C₆₀ in moderate yield (52%). Compounds 2 and 3 have been characterized by micro-analysis, spectroscopy, and single-crystal X-ray diffraction studies. A molecular structure determination reveals that complex 2 adopts a regular tetrahedral geometry with three edge-bridging CO groups around the basal triangle and a diphosphine κ²-Ph₂P(o- C₆H₄)PPh₂ ligand chelating one of the basal iridium atoms. In contrast, complex 3 possesses a butterfly geometry in which the C₆₀ ligand is coordinated to the lower wing of the butterfly by an arene type μ₃-η²: η²:η²-C₆₀ bonding mode. One unique feature of 3 is the presence of both ortho phosphorylated and ortho-metalated phenyl rings forming five-membered [Ir-P-C-C-P] and [Ir-Ir-P-C-C] metallocycles joined in a spiro union at the iridium-indium-bridged phosphorus atom. A crossover experiment confirms that the conversion of 1 to 2 is intramolecular. Plausible reaction pathways for the formation of 2 and 3 are proposed.

Full text of DOI:10.1021/om049303i

Organometallics 2005, 24, 675-679
675
Ortho Phosphorylation of PPh3 To Give a Diphosphine
and Formation of a “Butterfly” Structure on a
Tetrairidium Framework
Bo Keun Park,† Md. Arzu Miah,† Hongkyu Kang,† Kwangyeol Lee,†
Youn-Jaung Cho,† David G. Churchill,† Sangwoo Park,‡ Moon-Gun Choi,‡ and
Joon T. Park*,†
National Research Laboratory, Department of Chemistry and School of Molecular Science
(BK21), Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea, and
Department of Chemistry, Yonsei University, Seoul 120-749, Korea
Received September 7, 2004
A brief thermolysis of the bis-phosphine-substituted tetrairidium cluster Ir4(CO)10(PPh3)2
(1) in chlorobenzene (CB) converts it rapidly to the diphosphine cluster Ir4(CO)7(µ-CO)3{κ2-
Ph2P(o-C6H4)PPh2} (2) in 53% yield, providing evidence for ortho phosphorylation at the
tetrairidium cluster framework. Treatment of 2 with excess C60 affords the “butterfly”
Ir4-C60 complex Ir4(CO)6(µ-CO){µ3-κ2-Ph2P(o-C6H4)P(η1-o-C6H4)}(µ3-η2:η2:η2-C60) (3) in 71%
yield. Interestingly, compound 3 can be prepared directly from the thermolysis of 1 with
excess C60 in moderate yield (52%). Compounds 2 and 3 have been characterized by micro-
analysis, spectroscopy, and single-crystal X-ray diffraction studies. A molecular structure
determination reveals that complex 2 adopts a regular tetrahedral geometry with three edge-
bridging CO groups around the basal triangle and a diphosphine κ2-Ph2P(o-C6H4)PPh2 ligand
chelating one of the basal iridium atoms. In contrast, complex 3 possesses a “butterfly” geom-
etry in which the C60 ligand is coordinated to the lower wing of the “butterfly” by an arene
type µ3-η2 η2 η2-C60 bonding mode. One unique feature of 3 is the presence of both ortho
:
:
phosphorylated and ortho-metalated phenyl rings forming five-membered [Ir-P-C-C-P]
and [Ir-Ir-P-C-C] metallocycles joined in a spiro union at the iridium-iridium-bridged
phosphorus atom. A crossover experiment confirms that the conversion of 1 to 2 is
intramolecular. Plausible reaction pathways for the formation of 2 and 3 are proposed.
Introduction
reactions of C60 with phosphine-substituted metal clus-
ters such as Ir4(CO)9(PPh3)3,4 Ir4(CO)8(PMe3)4,5 and
Rh6(CO)12(dppm)2.6 As an extension of our studies on
the chemistry of C60-metal cluster complexes, we
examined the reaction between Ir4(CO)10(PPh3)2 (1) and
C60. Herein we report the full details of synthesis and
characterization of Ir4(CO)7(µ-CO)3{κ2-Ph2P(o-C6H4)-
PPh2} (2) formed by ortho phosphorylation of PPh3 and
Ir4(CO)6(µ-CO){µ3-κ2-Ph2P(o-C6H4)P(η1-o-C6H4)}(µ3-η2:
η2:η2-C60) (3) by stabilization of the “butterfly” structure
from the reaction of tetrahedral 1 with C60, as shown
in Scheme 1.
The extensive use of [60]fullerene, the most abundant
member of the fullerene family, as a ligand in organo-
metallic chemistry has been attributed to its pivotal role
in material science, owing to its unique electronic,
optical, and magnetic properties.1 In particular, the
interaction of a carbon cluster such as C60 with metal
clusters has been a topic of great interest in exohedral
metallofullerene chemistry,2 because C60-metal cluster
complexes have a direct analogy to carbon nanotubes
functionalized with metal nanoparticles.3 Furthermore,
C60-metal cluster complexes exhibit very strong elec-
tronic communication between C60 and metal-cluster
centers that can be fine-tuned by ligands attached to
the metal atoms.2a
Results and Discussion
Synthesis and Characterization of 2 and 3. Ther-
molysis of Ir4(CO)10(PPh3)2 (1) in chlorobenzene (CB) at
Metal clusters substituted with donor ligands are
commonly employed for the syntheses of C60-metal
cluster complexes, since C60 acts as an electron-with-
drawing ligand. In our previous work, we examined the
(2) (a) Lee, K.; Song, H.; Park, J. T. Acc. Chem. Res. 2003, 36, 78
and references therein. (b) Balch, A. L.; Olmstead, M. M. Chem. Rev.
1998, 98, 2123. (c) Stephens, A.; Green, M. L. H. Adv. Inorg. Chem.
1997, 44, 1.
(3) (a) Ye, X. R.; Lin, Y.; Wai, C. M. Chem. Commun. 2003, 642. (b)
Hermans, S.; Sloan, J.; Shephard, D. S.; Johnson, B. F. G.; Green, M.
L. H. Chem. Commun. 2002, 276.
(4) Park, B. K.; Miah, M. A.; Lee, G.; Cho, Y.-J.; Lee, K.; Park, S.;
Choi, M,-G.; Park, J. T. Angew. Chem., Int. Ed. 2004, 43, 1712.
(5) Lee, G.; Cho, Y.-J.; Park, B. K.; Lee, K.; Park, J. T. J. Am. Chem.
Soc. 2003, 125, 13920.
(6) (a) Lee, K.; Song, H.; Kim, B. S.; Park, J. T.; Park, S.; Choi, M.-
G. J. Am. Chem. Soc. 2002, 124, 2872. (b) Lee, K.; Choi, Y. J.; Cho,
Y.-J.; Lee, C. Y.; Song, H. J.; Lee, C. H.; Lee, Y. S.; Park, J. T. J. Am.
Chem. Soc. 2004, 126, 9837.
* To whom correspondence should be addressed. E-mail: joontpark@
kaist.ac.kr. Fax: + 82-42-869-5826.
† Korea Advanced Institute of Science and Technology.
‡ Yonsei University.
(1) (a) Makarova, T. L.; Sundqvist, B.; Ho¨hne, R.; Esquinazi, P.;
Kopelevich, Y.; Scharff, P.; Davydov, V. A.; Kashevarova, L. S.;
Rakhmanina, A. V. Nature 2001, 413, 716. (b) Imahori, H.; Norieda,
H.; Yamada, H.; Nishimura, Y.; Yamazaki, I.; Sakata, Y.; Fukuzumi,
S. J. Am. Chem. Soc. 2001, 123, 100. (c) Hutchison, K.; Schick, J.;
Rubin, Y.; Wudl, F. J. Am. Chem. Soc. 1999, 121, 5611.
10.1021/om049303i CCC: $30.25 © 2005 American Chemical Society
Publication on Web 01/15/2005

676 Organometallics, Vol. 24, No. 4, 2005
Park et al.
Scheme 1a
Scheme 2a
a Legend: (1) ortho phosphorylation, -C6H6; (2) rearrange-
ment of the diphosphine ligand; (3) ortho metalation; (4)
-C6H6; (5) -3 CO, +C60. Carbonyl and C60 ligands have been
omitted for clarity.
a Legend: (1) 2 equiv of C60, C6H5Cl, 132 °C, 2 h; (2) C6H5Cl,
132 °C, 10 min; (3) 2 equiv of C60, C6H5Cl, 132 °C, 2 h. Terminal
carbonyl ligands have been omitted for clarity.
p-C6H4CH3) in a 1:1 ratio, but crossover products,
Ir4(CO)7(µ-CO)3(PPh3)2{κ2-Ph2P(o-C6H4)P(p-tol)2} and
Ir4(CO)7(µ-CO)3(PPh3)2{κ2-Ph2P(o-C6H3CH3)P(p-tol)2},
were not detected. This observation suggests that the
transformation 1 f 2 is intramolecular. From this
mechanistic data, plausible reaction pathways for the
conversion 1 f 2 f 3 are proposed in Scheme 2. The
first step is an ortho phosphorylation in 1, which
involves activation of C-H and P-C bonds of the two
phenyl groups on the P1 and P2 atoms, respectively,
and subsequent elimination of benzene to form the
proposed intermediate A with the bridging diphosphine
κ2-Ph2P(o-C6H4)PPh2. The second step is a rearrange-
ment of the bridging diphosphine ligand from Ir1 to Ir4
to give the isolated intermediate 2. A similar structure
is precedented in Ir4(CO)10(1,2-bis(dimethylarsino)ben-
zene).8 Ortho metalation of a phenyl group on P2 in 2
results in the rupture of the Ir1-Ir4 bond to form the
proposed hydrido “butterfly” intermediate B (62 val-
ence electrons (VE)); this conversion was previously
reported in an Ir4 cluster.4 Binuclear reductive elimina-
tion of C6H6 at the Ir4 and P2 centers in B induces
coordination of the P2 atom to the Ir2 center in the
proposed intermediate C. The final product 3 is pro-
duced by the loss of three carbonyl groups from C
followed by µ3-η2:η2:η2-C60 coordination to one wing of
the “butterfly”.
In the transformation 1 f 2 f 3, two PPh3 ligands
are converted to the diphosphine κ2-Ph2P(o-C6H4)PPh2
and further to a µ3-κ2-Ph2P(o-C6H4)P(η1-o-C6H4) unit on
the Ir4 framework by successive ortho phosphoryla-
tion and ortho metalation, as illustrated in Scheme
2. Synthesis of phosphine ligands with P-(C)n-P
and P-(C)n-P-(C)n-P donor atom sequences is of
special interest because of their ability to bridge metal-
metal bonds and, thus, to stabilize oligometallic or metal
cluster complexes. Such phosphine ligands have previ-
ously been prepared by tedious multistep organic syn-
132 °C for ca. 10 min, followed by workup and chro-
matographic separation, afforded a major compound
containing a diphosphine ligand, Ir4(CO)7(µ-CO)3{κ2-
Ph2P(o-C6H4)PPh2} (2), in 53% yield, together with a
minor and unidentified band. When 2 was treated
with 2 equiv of C60 in refluxing CB for 2 h, the
Ir4-C60 derivative Ir4(CO)6(µ-CO){µ3-κ2-Ph2P(o-C6H4)P-
(η1-o-C6H4)}(µ3-η2:η2:η2-C60) (3) was obtained in high
yield (71%) as a black solid. Thermolysis of 2 without
C60 under similar conditions resulted only in extensive
decomposition. Interestingly, the reaction of 1 with C60
produced 3 directly in moderate yield (52%), after the
reaction mixture was refluxed in CB for 2 h. This
implies that 2 is an intermediate for product 3. The
synthetic details for 2 and 3 are given in Scheme 1.
The IR spectra of 2 and 3 exhibit two bridging CO
bands at 1855 and 1799 cm-1 and one band at 1827
cm-1, respectively, consistent with structural assign-
1
ments (vide infra). The H NMR spectrum of 2 shows
multiplets at δ 7.56, 7.51, and 7.35-7.24 assigned to
aromatic protons. The signals at δ 7.56 and 7.51
correspond to four o-phenylene group protons, and the
signals at δ 7.35-7.24 are assigned to the phenyl group
protons. Similar chemical shifts for the four protons of
the o-phenylene bridge (ca. δ 7.58) are observed in
1
Pd{κ2-Ph2P(o-C6H4)PPh2}Br2 (4).7 The H NMR spec-
trum of 3 shows multiplets in the aromatic region at
δ 7.69-7.36 assigned to phenyl group protons. The
31P{1H} NMR spectrum of 2 shows a singlet at δ 23.2
for the two magnetically equivalent phosphorus atoms
of the diphosphine ligand (cf. δ 64.2 in 4).7 The 31P{1H}
NMR spectrum of 3 contains two singlets at δ 182.2 and
25.1 for the two phosphorus atoms. The former is as-
signed to the bridging phosphorus atom, commonly ob-
served in the downfield region (δ 130-300).4 The sing-
let at δ 25.1 is consistent with a terminal phosphorus
atom bonded to an iridium center (δ -30 to +70).4
Unfortunately, the mass spectrum of 3 could not be
obtained.
(7) Estevan, F.; Garc´ıa-Bernabe´, A.; Lahuerta, P.; Sanau´, M.;
Ubeda, M. A.; Galan-Mascaros, J. R. J. Organomet. Chem. 2000, 596,
248.
(8) Shapley, J. R.; Stuntz, G. F.; Churchill, M. R.; Hutchinson, J. P.
J. Am. Chem. Soc. 1979, 101, 7425.
A crossover experiment was carried out employing
Ir4(CO)10(PPh3)2 (1) and Ir4(CO)10(P(p-tol)3)2 (p-tol )

Ortho Phosphorylation of PPh3
Organometallics, Vol. 24, No. 4, 2005 677
Table 1. Crystal and Structural Determination
Data for 2 and 3
2
3‚CS2
formula
fw
C
40H24Ir4O10P2
C
91H18Ir4O7P2‚CS2
1495.33
triclinic
P1h
2129.92
monoclinic
P21/n
syst
space group
a, Å
b, Å
c, Å
10.6813(9)
12.406(1)
16.709(1)
75.039(1)
85.648(2)
70.834(2)
2020.4(3)
2
2.458
293(2)
0.71073
13.267
16.301(3)
24.121(5)
17.570(4)
90
107.518(4)
90
6588(2)
4
2.147
293(2)
0.71073
8.232
1.49, 25.54
0.0813
0.2001
1.141
R, deg
â, deg
γ , deg
V, Å3
Z
Dcalcd, Mg m-3
temp, K
λ(Mo KR), Å
µ, mm-1
θ
RF
Rw
min, θmax, deg
1.92, 27.99
0.0540
0.1206
1.082
a
b
GOF
a RF ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
2
Figure 1. Molecular structure of 2.
Table 2. Selected Interatomic Distances (Å) and
Angles (deg) with Esd’s for 2
Table 3. Selected Interatomic Distances (Å) and
Angles (deg) with Esd’s for 3
Bond Distances
Bond Distances
Ir(1)-Ir(2)
Ir(2)-Ir(3)
Ir(3)-Ir(4)
Ir(1)-P(1)
P(1)-C(301)
C(301)-C(306)
2.7715(6)
2.6974(6)
2.7099(6)
2.287(3)
1.85(1)
Ir(1)-Ir(3)
Ir(2)-Ir(4)
Ir(1)-Ir(4)
Ir(1)-P(2)
P(2)-C(306)
2.7683(6)
2.7175(6)
2.7500(6)
2.296(3)
1.82(1)
Ir(1)-Ir(2)
Ir(2)-Ir(3)
Ir(3)-Ir(4)
Ir(4)-P(2)
Ir(1)-C(2)
Ir(2)-C(4)
Ir(3)-C(6)
P(2)-C(401)
C(301)-C(306)
C(1)-C(2)
C(2)-C(3)
C(4)-C(5)
Ir(1)-C(406)
2.759(1)
2.888(1)
2.757(1)
2.272(5)
2.26(2)
2.25(2)
2.18(2)
1.80(2)
1.36(3)
1.43(3)
1.51(2)
1.48(2)
2.07(2)
Ir(1)-Ir(3)
Ir(2)-Ir(4)
Ir(4)-P(1)
Ir(1)-C(1)
Ir(2)-C(3)
Ir(3)-C(5)
P(1)-C(301)
P(2)-C(306)
C(401)-C(406)
C(1)-C(6)
C(3)-C(4)
C(5)-C(6)
2.845(1)
2.789(1)
2.320(5)
2.30(2)
2.16(2)
2.20(2)
1.85(2)
1.83(2)
1.44(3)
1.47(2)
1.45(3)
1.48(2)
1.37(2)
Bond Angles
Ir(4)-Ir(1)-Ir(3)
Ir(3)-Ir(1)-Ir(2)
Ir(3)-Ir(2)-Ir(1)
Ir(2)-Ir(3)-Ir(4)
Ir(4)-Ir(3)-Ir(1)
Ir(3)-Ir(4)-Ir(1)
P(1)-Ir(1)-P(2)
P(2)-Ir(1)-Ir(4)
P(2)-Ir(1)-Ir(3)
P(2)-Ir(1)-Ir(2)
58.82(1) Ir(4)-Ir(1)-Ir(2)
58.28(1) Ir(3)-Ir(2)-Ir(4)
60.80(1) Ir(4)-Ir(2)-Ir(1)
60.34(2) Ir(2)-Ir(3)-Ir(1)
60.25(2) Ir(3)-Ir(4)-Ir(2)
60.93(1) Ir(2)-Ir(4)-Ir(1)
58.97(1)
60.06(2)
60.12(2)
60.92(2)
59.60(2)
60.91(2)
108.90(7)
144.24(7)
148.69(7)
82.5(1)
P(1)-Ir(1)-Ir(4)
Bond Angles
168.32(7) P(1)-Ir(1)-Ir(3)
110.40(7) P(1)-Ir(1)-Ir(2)
Ir(2)-Ir(1)-Ir(3)
Ir(3)-Ir(2)-Ir(1)
Ir(2)-Ir(3)-Ir(4)
Ir(4)-Ir(3)-Ir(1)
P(2)-Ir(4)-P(1)
P(1)-Ir(4)-Ir(3)
C(401)-P(2)-Ir(4)
C(301)-P(1)-Ir(4)
62.01(3) Ir(3)-Ir(2)-Ir(4)
60.47(3) Ir(4)-Ir(2)-Ir(1)
59.18(3) Ir(2)-Ir(3)-Ir(1)
107.60(3) Ir(2)-Ir(4)-Ir(3)
84.3(2) P(2)-Ir(4)-Ir(3)
166.0(1) C(306)-P(2)-Ir(2)
131.1(7) C(306)-P(2)-Ir(4)
58.07(3)
109.15(3)
57.52(3)
62.75(3)
83.4(1)
114.1(6)
110.7(6)
112.54(7) Ir(1)-P(1)-C(301) 105.7(3)
Ir(1)-P(1)-C(306) 106.1(4)
thesis.9 Instances of phosphine coupling to form a
diphosphine on a metallic framework are rare, with two
examples for Pd7 and Ir4 having been previously re-
ported.
108.7(6) C(406)-C(401)-P(2) 120(1)
C(306)-C(301)-P(1) 118(2)
C(301)-C(306)-P(2) 118(1)
X-ray Crystal Structures of 2 and 3. Details of the
crystallographic data for 2 and 3 are summarized in
Table 1. Selected interatomic distances and angles of 2
and 3 are listed in Tables 2 and 3, respectively.
The molecular structure of 2 is shown in Figure 1.
Compound 2 adopts a tetrahedral geometry (60 VE)
containing 10 carbonyl groups and one diphosphine
ligand. The basal triangle, Ir(1)-Ir(2)-Ir(3), has two
long bonds (Ir(1)-Ir(2) ) 2.7715(6) Å and Ir(1)-Ir(3) )
2.7683(6) Å) and one short bond (Ir(2)-Ir(3) )
2.6974(6) Å). However, the average iridium-iridium
distance of 2.736(6) Å is comparable to that found in
previously reported tetrahedral complexes (2.739 Å).10
The basal triangle accommodates three bridging CO
groups. Furthermore, the Ir(1) atom is chelated by the
κ2-P(o-C6H4)P ligand, a four-electron donor. The P(1)
atom is lying almost in the basal plane, whereas P(2)
lies below the plane, forming the five-membered met-
allacycle Ir(1)-P(1)-C(301)-C(306)-P(2). Overall struc-
tural features of 2 are similar to those of Ir4(CO)10(1,2-
bis(dimethylarsino)benzene).8
The molecular structure of 3 is depicted in Figure 2.
Compound 3 reveals a “butterfly” geometry (62 VE) to
which seven carbonyl groups (six terminal and one
bridging), a µ3-η2:η2:η2-C60 group, and a bridging diphos-
phine ligand are coordinated. The bond length of the
Ir(2)-Ir(3) “hinge” is 2.888(1) Å, relatively longer than
the Ir-Ir bond distances in the two “wings”. However,
the average iridium-iridium bond distance of 2.808(1)
Å is comparable to those observed in other “butterfly”
tetrairidum clusters.11 The Ir(1)-Ir(2) edge is asym-
metrically bridged by a carbonyl ligand. The P(1) atom
(9) (a) Bianchini, C.; Frediani, P.; Sernau, V. Organometallics 1995,
14, 5458. (b) Hietkamp, S.; Sommer, H.; Stelzer, O. Inorg. Synth. 1989,
25, 120. (c) Hartley, J. G.; Venanzi, L. M.; Goodall, D. C. J. Chem.
Soc. 1963, 3930.
(10) Pergola, R. D.; Garlaschelli, L.; Martinengo, S.; Manassero, M.;
Sansoni, M. J. Organomet. Chem. 2000, 593, 63.

678 Organometallics, Vol. 24, No. 4, 2005
Park et al.
markable coupling reaction of phosphines on Ir4 carbo-
nyl clusters.
Experimental Section
General Comments. All reactions were carried out under
a nitrogen atmosphere with use of standard Schlenk tech-
niques. Solvents were dried over the appropriate drying agents
and distilled immediately before use. C60 (99.5%, SES Re-
search), Ir4(CO)12 (98%, Strem), PPh3 (99%, Aldrich), and KOH
(85%, Junsei) were used without further purification. Ir4(CO)10-
(PPh3)2 was prepared according to the literature method.12
Preparative thin-layer chromatography (TLC) plates were
produced with GF254 silica gel (type 60, E. Merck). Infrared
spectra were obtained on a Bruker EQUINOX-55 FT-IR
spectrophotometer. 1H NMR (400 MHz) spectra were recorded
on a Bruker AVANCE-400 spectrometer, and 31P NMR (122
MHz) spectra were recorded on a Bruker AM-300 spectrom-
eter. Positive ion FAB mass spectra (FAB+) was obtained by
the staff of the Korea Basic Science Center, and the m/z value
was referenced to 193Ir. Elemental analyses were provided by
the staff of the Energy and Environment Research Center at
KAIST.
Preparation of Ir4(CO)7(µ-CO)3{K2-Ph2P(o-C6H4)PPh2}
(2). A chlorobenzene solution (30 mL) of Ir4(CO)10(PPh3)2
(1; 30 mg, 0.019 mmol) was heated at reflux for 10 min.
Evaporation of the solvent and purification by preparative TLC
(CH2Cl2/C6H14, 1/1) gave 2 (15.1 mg, 0.010 mmol, 53%, Rf )
0.7) as an orange solid: IR (C6H12) ν(CO) 2071 (m), 2040 (s),
2002 (m), 1992 (w), 1981 (w), 1855 (w), 1799 (w) cm-1; 1H NMR
(400 MHz, CDCl3, 298 K) δ 7.56 (m, 2H), 7.51 (m, 2H), 7.35-
7.24 (m, 20H) (all C6H5 + C6H4); 31P{1H} NMR (122 MHz,
CDCl3, 298 K) δ 23.2 (s); MS (FAB+) m/z 1496 [M+]. Anal. Calcd
for C40H24Ir4O10P2: C, 32.13; H, 1.62. Found: C, 31.95; H, 1.50.
Preparation of Ir4(CO)6(µ-CO){µ3-K2-Ph2P(o-C6H4)P(η1-
o-C6H4)}(µ3-η2:η2:η2-C60) (3). A chlorobenzene solution (30 mL)
of 1 (30 mg, 0.019 mmol) and C60 (2 equiv, 27 mg, 0.038 mmol)
was heated at reflux for 2 h. Evaporation of the solvent and
purification by preparative TLC (CS2/CH2Cl2, 8/1) afforded
compound 3 (20.3 mg, 0.010 mmol, 52%, Rf ) 0.6) as a black
solid: IR (CH2Cl2) ν(CO) 2053 (vs), 2019 (vs), 2002 (vs), 1979
(sh), 1827 (w) cm-1; 1H NMR (400 MHz, CDCl3, 298 K) δ 8.89
(m, phenyl, 1H), 8.09 (m, phenyl, 2H), 7.69-7.36 (m, phenyl,
15H); 31P NMR (122 MHz, C6D4Cl2, 298 K) δ 182.2 (s, 1P), 25.1
(s, 1P). Anal. Calcd for C91H18Ir4O7P2: C, 53.21; H, 0.88.
Found: C, 53.04; H, 0.83.
Figure 2. Molecular structure of 3.
with two phenyl groups is axially coordinated to the
Ir(4) atom. The P(2) atom is bridging the Ir(2) and
Ir(4) edge, and a phenyl group on the P(2) atom has
undergone ortho metalation to form a five-membered
Ir(1)-Ir(2)-P(2)-C(401)-C(406) metallacycle. The
µ3-κ2-Ph2P(o-C6H4)P(η1-o-C6H4) ligand now acts as a six-
electron donor, resulting in a “butterfly” geometry. The
C60 ligand is coordinated to the lower “wing” of the
“butterfly” composed of the Ir(1)-Ir(2)-Ir(3) triangle in
a typical µ3-η2:η2:η2-C60 arene-type fashion, which has
recently been reviewed.2a All bond lengths and angles
for 2 and 3, including those for the carbonyl and C60
ligands, are within the expected ranges.
Reaction of 2 with C60. A chlorobenzene solution (30 mL)
of 2 (30 mg, 0.020 mmol) and C60 (2.1 equiv, 30 mg, 0.042
mmol) was heated at reflux for 1.5 h. Evaporation of the
solvent and purification by preparative TLC (CS2/CH2Cl2, 8/1)
produced compound 3 (29.2 mg, 0.014 mmol, 71%, Rf ) 0.6)
as a black solid.
Crystal Structure Determination. Crystals of 2 and 3
suitable for X-ray diffraction studies were obtained by an
interlayer diffusion technique (methanol into a CH2Cl2 solution
of 2; heptane into a CS2 solution of 3). Diffraction data were
collected on a Siemens SMART diffractometer/CCD area
detector. Preliminary orientation matrix and cell constants
were determined from three series of ω scans at different
starting angles. Each series consisted of 15 frames collected
at scan intervals of 0.3° in ω with an exposure time of 10 s
per frame. A total of 12 533 (at 293 K) and 34 548 (at 293 K)
data were collected for 2 and 3, respectively. Total reflections
were corrected for Lorentz and polarization effects, but no
correction for crystal decay was applied. Each structure was
solved by direct13 and difference Fourier methods and was
Concluding Remarks
In the transformation 1 f 2 f 3, two PPh3 ligands
are converted to the diphosphine κ2-Ph2P(o-C6H4)PPh2
(for 2) and in turn to µ3-κ2-Ph2P(o-C6H4)P(η1-o-C6H4)
(for 3) on the Ir4 cluster framework by successive
ortho phosphorylation and ortho metalation processes.
The “butterfly” structure of 3 is apparently stabi-
lized by the multifunctional C60 ligand. A crossover
experiment implies that the conversion 1 f 2 is an
intramolecular reaction. Thus, plausible reaction path-
ways for the formation of 2 and 3 have been pro-
posed. We are currently investigating facile synthetic
methods for multifunctional phosphines from this re-
(11) (a) Stuntz, G. F.; Shapley, J. R.; Pierpont, C. G. Inorg. Chem.
1978, 17, 2596. (b) Vargas, M. D.; Pereira, R. M. S.; Braga, D.; Grepioni,
F. J. Chem. Soc., Chem. Commun. 1993, 1008. (c) Benvenutti, M. H.
A.; Vargas, M. D.; Braga, D.; Grepioni, F.; Parisini, E.; Mann, B. E.
Organometallics 1993, 12, 2955 and references therein. (d) Pereira,
R. M. S.; Fijiwara, F. Y.; Vargas, M. D.; Braga, D.; Grepioni, F.
Organometallics 1997, 16, 4833. (e) Araujo, M. H.; Hitchcock, P. B.;
Nixon, J. F.; Vargas, M. D. J. Braz. Chem. Soc. 1998, 9, 563.
(12) (a) Albano, V.; Bellon, P.; Scatturin, V. Chem. Commun. 1967,
730. (b) Sonnenberger, D. C.; Atwood, J. D. Organometallics 1982, 1,
694.
(13) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.

Ortho Phosphorylation of PPh3
Organometallics, Vol. 24, No. 4, 2005 679
refined by full-matrix least-squares methods based on F2
(SHELX 97).14 All non-hydrogen atoms were refined with
anisotropic thermal coefficients. Details of relevant crystal-
lographic data are summarized in Table 1.
Ministry of Science & Technology of Korea (MOST) and
the Korea Science & Engineering Foundation (Project
No. 1999-1-122-001-5).
Supporting Information Available: Figures and tables
giving full crystallographic and structural data for 2 and 3.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. This work was supported by the
National Research Laboratory (NRL) Program of the
(14) Sheldrick, G. M. SHELX97, Program for Crystal Structure
Refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
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