Novel [60]fullerene-assisted ortho-phosphanation on a tetrairidium butterfly framework

Article abstract of DOI:10.1002/anie.200353290

A mono- to di- and triphosphane transformation occurs on treatment of [Ir₄(CO)₉(PPh₃)₃] (1) with C ₆₀ to successively afford 2 and 3. The noninnocent, multifunctional C₆₀ ligand plays a crucial role in transforming three PPh₃ ligands into a μ₃-PPh₂(o-C₆H₄) P(o-C₆H₄) PPh(η¹-o-C₆H ₄) triphosphane ligand by a series of ortho-phosphanation and ortho-metalation processes on the Ir₄ cluster framework.

Full text of DOI:10.1002/anie.200353290

Communications
examined the reaction between the phosphane-substituted
iridium carbonyl cluster [Ir4(CO)9(PPh3)3] (1)[4] and C60. We
demonstrated a new behavior of C60 as a noninnocent ligand,
stemming from its multifunctionality, for the chemical trans-
formation of ligands on the cluster surface. Here we report a
novel C60-induced formation of a P-(C)n-P-(C)n-P moiety by a
series of ortho-phosphanation and ortho-metalation reactions
of phosphanes on
(Scheme 1).
a tetrairidium butterfly framework
Phosphane Ligands
Novel [60]Fullerene-Assisted ortho-
Phosphanation on a Tetrairidium Butterfly
Framework**
Bo Keun Park, M. Arzu Miah, Gaehang Lee,
Youn-Jaung Cho, Kwangyeol Lee, Sangwoo Park,
Moon-Gun Choi, and Joon T. Park*
The extensive use of [60]fullerene, the most abundant
member of the fullerene family, as a ligand in organometallic
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 decorated with metal nanoparticles.[3] Further-
more, they exhibit very strong electronic communication
between C60 and metal-cluster centers that can be fine-tuned
by ligands attached to the metal atoms.[2a] As part of our
studies on the chemistry of C60–metal cluster complexes, we
Scheme 1. a) 2 equiv C60, ClC6H5, 1328C, 3 h, 36%; b) ClC6H5, 1328C,
40 min, 64%; c) 2 equiv C60, ClC6H5, 1328C, 3 h, 41%.
Heating a mixture of 1 and 2 equiv of C60 in refluxing
chlorobenzene (CB) for 2 h afforded [Ir4(CO)6{m3-PPh2(o-
C6H4)P(o-C6H4)PPh(h1-o-C6H4)}(m3-h2:h2:h2-C60)] (3) in mod-
erate yield (36%). Thermolysis of 1 in refluxing CB gave
[Ir4(CO)8{m-PPh2(o-C6H4)PPh}{m3-PPh2(h1:h2-o-C6H4)}] (2) in
64% yield. Reaction of 2 with C60 in refluxing CB produced 3
in 41% yield, that is, 2 is indeed the reaction intermediate for
the final product 3 (see Scheme 1 and Experimental Section).
The formulas of 2 and 3 were established by microanalytical
data and molecular-ion isotope multiplets at m/z 1624 for 2
and 2210 for 3 in the positive-ion FAB mass spectra.
[*] B. K. Park, Dr. M. A. Miah, G. Lee, Y.-J. Cho, Prof. J. T. Park
National Research Laboratory,
The molecular structures of 2 and 3 are shown in Figures 1
and 2, respectively. Both complexes exhibit a butterfly
geometry of four iridium atoms, in which the two wings are
nearly perpendicular to each other, as was observed in
previously reported wingtip-bridged Ir4 butterfly complexes.[5]
The P1 atom bearing two phenyl groups in 2 is coordinated to
the Ir4 center, and the two wingtip Ir atoms are almost
symmetrically bridged by the P2 atom. An o-phenylene group
bridges the P1 and P2 atoms in the bidentate diphosphane
moiety Ph2P(o-C6H4)PPh, which in turn forms a five-mem-
bered metallacyclic P1-C301-C306-P2-Ir4 moiety on the
cluster. Another interesting structural feature of 2 is the
presence of a m3-PPh2(h1:h2-o-C6H4) ligand (a five-electron
Department of Chemistry and School of Molecular Science (BK 21)
Korea Advanced Institute of Science and Technology
Daejeon, 305-701 (Korea)
Fax: (+82)42-869-5826
E-mail: joontpark@kaist.ac.kr
Prof. K. Lee
Department of Chemistry, Korea University
Seoul, 136-701 (Korea)
S. Park, Prof. M.-G. Choi
Department of Chemistry and Molecular Structure Laboratory
Yonsei University, Seoul, 120-749 (Korea)
[**] This research was supported by the National Research Laboratory
(NRL) Program of the Korean Ministry of Science & Technology
(MOST), the Korea Science & Engineering Foundation (KOSEF,
Project No. 1999-1-122-001-5) for J.T.P., and a Korea University
Grant for K.L.
donor), which is coordinated through P3 to the Ir3 atom by an
2
ꢀ
Ir C(phenylene) s bond to the Ir2 center, and by an h
interaction of the o-C6H4 ring to the Ir1 atom. A similar
bonding mode was previously observed in [(m-H)-
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
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DOI: 10.1002/anie.200353290
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Angewandte
Chemie
Os3(CO)8{m3-PPhMe(h1:h2-C6H4)}][6] and [(m-H)Ru3(CO)8-
{m3-PPh(h1:h2-C6H4)(h-C5H4)Fe(h-C5H4PPh2)}].[7] In 3, the
P1 atom bearing two phenyl groups is coordinated to the
Ir4 atom, and the P2 atom bridges the two wingtip Ir1 and Ir4
atoms similarly to 2. The phenyl group on the P2 atom has
been ortho-phosphanated by the P3 atom, and a phenyl group
on the P3 center underwent ortho-metalation to form five-
membered Ir1-P2-C401-C406-P3 and Ir1-Ir2-C502-C501-P3
metallacycles, respectively. Overall, the three PPh3 ligands in
1 are converted to a triphosphane ligand Ph2P(o-C6H4)P(o-
1
2
2
2
ꢀ
C6H4)PPh(h -o-C6H4) in 3. The C C bonds in the m3-h :h :h -
60 ligand alternate in length, with an average long distance of
C
1.49(1) and an average short distance of 1.43(1) Š. This face-
capping C60 bonding mode is well documented for a variety of
cluster frameworks.[2a]
A plausible reaction mechanism for 1!2!3 is proposed
in Scheme 2. The first step is an ortho-phosphanation in 1 to
form intermediate A. ortho-Metalation of a phenyl group on
Figure 1. Molecular structure with atomic labeling scheme for 2.
ꢀ
ꢀ
Selected bond lengths [Š] and angles [8]: Ir1 Ir2 2.6953(6), Ir1 Ir3
ꢀ
ꢀ
ꢀ
ꢀ
2.7170(7), Ir2 Ir3 2.6689(6), Ir2 Ir4 2.7409(6), Ir3 Ir4 2.8054(6), Ir1
ꢀ
ꢀ
C701 2.55(1), Ir1 C706 2.41(1), Ir2 C706 2.08(1); Ir1-Ir2-Ir4 88.20(2),
Ir1-Ir3-Ir4 86.46(2).
Scheme 2. a) ꢀC6H6; b) ortho-metalation of a phenyl group on P3;
c) ꢀC6H6, ꢀCO; d) +C60; e) ꢀC6H6; f) ꢀ2CO.
ꢀ
the P3 atom in A results in rupture of the Ir1 Ir4 bond to
form the hydrido butterfly intermediate B (62 valence
electrons). Binuclear reductive elimination of C6H6 and the
loss of a carbonyl ligand in B induces coordination of the P2
atom to the Ir4 center and p coordination of the ortho-
metalated phenyl ring to form an h1:h2-o-C6H4 moiety in 2.
ꢀ
The next step is cleavage of the Ir3 P3 bond and subsequent
coordination of h2-C60 to produce intermediate C. Another
ortho-phosphanation reaction in C takes place to form a
triphosphane moiety, and the p interaction in the h1:h2-o-C6H4
ligand is replaced by coordination of the P3 atom to the Ir1
center to give intermediate D. The final product 3 is produced
by the loss of two carbonyl ligands and face-capping of the C60
ligand in the m3-h2:h2:h2 fashion.
Figure 2. Molecular structure with atomic labeling scheme for 3.
ꢀ
ꢀ
Selected bond lengths [Š] and angles [8]: Ir1 Ir2 2.7598(8), Ir1 Ir3
ꢀ
ꢀ
ꢀ
ꢀ
2.7827(8), Ir2 Ir3 2.8059(7), Ir2 Ir4 2.7401(9), Ir3 Ir4 2.8094(7), Ir2
C502 2.089(8); Ir1-Ir2-Ir4 85.02(1), Ir1-Ir3-Ir4 83.30(2).
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Communications
298 K): d = 7.14–8.07 (m, 24H); 6.78–6.93 ppm (m, 3H) (all C6H5 +
C6H4); 13C NMR (100 MHz, C6D4Cl2, 298 K): d = 188.4 (d, 1CO, JPC
2.5 Hz), 187.3 (d, 1CO, JPC = 3.2 Hz), 179.9 (s, 1CO), 173.3 (t, 1CO,
PC = 3.9 Hz), 172.4 (d, 1CO, JPC = 12.2 Hz), 161.2 (dd, 1CO, JPC
51.2 Hz, JPC = 5.5 Hz), 158.9–143.6 (54C, C60 sp2 region), 79.1 (d, 1C,
PC = 6.3 Hz, C60 sp3 p-bonded C) 68.0 (t, 1C, JPC = 4.9 Hz, C60 sp3 p-
In the transformation 1!2!3, three PPh3 ligands are
=
converted to the diphosphane m2-Ph2P(o-C6H4)PPh and in
turn to the triphosphane m3-PPh2(o-C6H4)P(o-C6H4)PPh(h1-o-
C6H4) on the Ir4 cluster framework by successive ortho-
phosphanation and ortho-metalation processes, as described
in Scheme 2. Synthesis of phosphane ligands with P-(C)n-P
and P-(C)n-P-(C)n-P donor sequences is of special interest,
because of their ability to bridge metal–metal bonds and thus
to stabilize oligometallic or metal cluster complexes. Such
phosphane ligands have usually been prepared by tedious
multistep organic synthesis.[8] We have now demonstrated that
facile ortho-phosphanation and ortho-metalation can take
place on an Ir4 framework and, more importantly, the
multifunctional C60 ligand can assist the ortho-phosphanation
step, as in the conversion of 2 to 3. To the best of our
knowledge, this is the first example not only of facile ortho-
phosphanation on transition metals but also of the C60
molecule acting as a noninnocent ligand that assists unusual
phosphane-transformation reactions.
J
=
J
bonded C), 64.1 (d, 1C, JPC = 2.4 Hz, C60 sp3 p-bonded C), 62.7 (s, 1C,
C60 sp3 p-bonded C), 61.2 (d, 1C, JPC = 4.5 Hz, C60 sp3 p-bonded C),
60.6 ppm (dd, 1C, JPC = 13.8 Hz, JPC = 2.3 Hz, C60 sp3 p-bonded C);
31P{H} NMR (122 MHz, CS2/ext. CD2Cl2, 298 K): d = 31.2 (d, 1P,
3JPP = 12.8 Hz), ꢀ16.3 (dd, 1P, 3JPP = 12.8 Hz, 3JPP = 4.0 Hz),
ꢀ21.5 ppm (d, 1P, 3JPP = 4.0 Hz); MS (FAB+): m/z: 2210 [M+].
X-ray crystal data for 3: Greenish black crystals were obtained by
slow diffusion of heptane into a solution of 3 in CS2 at room
temperature. The crystal used for data collection contained four
molecules of CS2 (C102H27P3O6Ir4·4CS2, Mr = 2210.09): monoclinic,
space group P21/c, Z = 4, 1calcd = 2.141 gcmꢀ3, a = 17.472(5), b =
3
20.071(6), c = 22.639(6) Š, b = 100.739(5)8, V= 7800(4) Š . The struc-
ture was solved by direct methods and refined by full-matrix least-
squares analysis to give R = 0.0422 and Rw = 0.0859 (based on F2) for
1144 parameters and 14530 unique reflections with I > 2s(I) and
1.69 < q < 25.528. Data was collected at T= 293(2) K.
We are currently investigating the detailed mechanistic
pathways of 1!2!3 and trying to develop facile synthetic
methods for multifunctional phosphanes from coupling
reactions of phosphanes on Ir4 carbonyl clusters in the
presence of C60 and dihydrogen.
Received: November 10, 2003 [Z53290]
Keywords: cluster compounds · fullerenes · iridium ·
.
phosphanation · Pligands
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Experimental Section
Details on the synthesis as well as a full spectroscopic characterization
of 2 and 3 and the conversion of 2 to 3 are given in the Supporting
Information. X-ray structural data were collected on
a CCD
diffractometer with MoKa radiation (l = 0.71073 Š) using w scans.
CCDC-221530 (2) and CCDC-221531 (3) contain the supplementary
crystallographic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB21EZ, UK; fax: (+ 44)1223-336-033; or deposit@ccdc.cam.
ac.uk).
2: Elemental analysis (%) calcd for C50H33Ir4O8P3: C 36.99, H
2.05; found: C 36.76, H 2.19; IR (C6H12): n˜(CO) = 2062 (w), 2049 (s),
2029 (vs), 2011 (vs), 1993 (vs), 1956 (m), 1946 cmꢀ1 (m); 1H NMR
[4] A. J. Drakesmith, R. Whyman, J. Chem. Soc. Dalton Trans. 1973,
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[8] a) C. Bianchini, P. Frediani, V. Sernau, Organometallics 1995, 14,
5458 – 5459; b) S. Hietkamp, H. Sommer, O. Stelzer, Inorg. Synth.
1989, 25, 120 – 122; c) J. G. Hartley, L. M. Venanzi, D. C. Goodall,
J. Chem. Soc. 1963, 3930 – 3936.
(400 MHz, CDCl3, 298 K): d = 8.44 (dd, 1H, JPH = 8.0 Hz, JPH
=
2.5 Hz), 7.89 (m, 1H), 7.63 (m, 4H), 7.46–6.88 (m, 24H), 6.62 (m,
2H), 6.51 ppm (t, 1H, JPH = 7.6 Hz) (all C6H5 + C6H4); 13C NMR
(100 MHz, CDCl3, 298 K): d = 186.8 (s, 1CO), 185.7 (s, 1CO), 179.6 (s,
1CO), 176.4 (s, 1CO), 166.4(s, 1CO), 165.7 (s, 1CO), 165.5 (d, 1CO,
2JCP = 3.5 Hz), 163.7 (d, 1CO, 2JCP = 4 Hz), 153.2–124.3 (42C, C6H5 +
C6H4); 31P{H} NMR (122 MHz, CDCl3, 298 K): d = 24.2 (d, 1P, 3JPP
=
22.1 Hz), 16.4 (s, 1P), ꢀ42.9 (d, 1P, 3JPP = 22.1 Hz); MS (FAB+): m/z:
1624 [M+].
X-ray crystal data for 2: Orange crystals were obtained by slow
diffusion of methanol into a solution of 2 in CH2Cl2 at room
temperature. The crystal used for data collection contained no solvent
¯
molecules (C50H33P3O8Ir4, Mr = 1623.47): triclinic, space group P1,
Z = 2, 1calcd = 2.256 gcmꢀ3
,
a = 11.087(1), b = 11.472(1), c =
21.576(2) Š, a = 91.925(2), b = 101.719(2), g = 116.070(1)8, V=
2390.1(4) Š3. The structure was solved by direct methods and refined
by full-matrix least-squares analysis to give R = 0.0576 and Rw =
0.1476 (based on F2) for 586 parameters and 10924 unique reflections
with I > 2s(I) and 1.95 < q < 28.028. Data was collected at T=
293(2) K.
3: Elemental analysis (%) calcd for C102H27Ir4O6P3: C 55.43, H
1.23; found: C 55.64, H 1.42. IR (CH2Cl2): n˜(CO) = 2045 (vs), 2016
(vs), 1998 (s), 1985 (sh), 1970 cmꢀ1 (m); 1H NMR (400 MHz, CDCl3,
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Angew. Chem. Int. Ed. 2004, 43, 1712 –1714