Synthesis of an unprecedented bicapped adamantoid [Cu6(μ 2-I)(μ3-I)4(μ4-I)(m-tolyl 3P)4(CH3CN)2] cluster

Article abstract of DOI:10.1021/ic049903+

The reaction of copper(I) iodide with tri-m-tolylphosphine (m-tolyl ₃P) in acetonitrile yielded the cluster [Cu₆(μ ₂-I)(μ₃-I)₄(μ₄-I)(m-tolyl ₃P)₄(CH₃CN)₂] (1), with a bicapped adamantoid geometry. In this compound, four Cu atoms are coordinated to four terminally bonded m-tolyl₃P ligands, two Cu atoms are bonded to two CH₃CN ligands, and iodide ligands have μ₂-I, μ₃-I, and μ₄-I bonding modes. This compound has four Cul₃P and two Cul₃N cores, and geometry around each Cu center is distorted tetrahedral. The polarizable iodide ligand and the position of the methyl group in the phenyl ring attached to the P atom appear to have played the pivotal role in the formation of monomeric bicapped adamantoid geometry, which is unique in copper chemistry.

Full text of DOI:10.1021/ic049903+

Inorg. Chem. 2004, 43, 3766−3767
Synthesis of an Unprecedented Bicapped Adamantoid
[Cu6(µ2-I)(µ3-I)4(µ4-I)(m-tolyl3P)4(CH CN)2] Cluster
3
,†
Tarlok S. Lobana,* Parminderjit Kaur,† and Takanori Nishioka‡
Department of Chemistry, Guru Nanak DeV UniVersity, Amritsar 143 005, India,
and Department of Materials Science, Graduate School of Science, Osaka City UniVersity,
Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
Received January 24, 2004
The reaction of copper(I) iodide with tri-m-tolylphosphine (m-tolyl3P)
in acetonitrile yielded the cluster [Cu (µ2-I)(µ3-I)4(µ4-I)(m-tolyl3P)4(CH -
CN)2] (1), with a bicapped adamantoid geometry. In this compound,
However, for compounds 3 and 4, cubane isomers are also
known.1d Triethylarsine also formed a cluster, [(Et3As)CuI]4
6
3
(13), with cubane structure, similar to that of 7.2b
As a part of our research activity to understand the
formation of clusters, or polymeric networks, with transition
metals,5,6 we decided to observe the effect of the position of
the methyl group in the phenyl ring, attached to the P atom,
and thus carried out reactions of tritolylphosphines with
copper(I) iodide in acetonitrile. The construction of supramo-
lecular metal complexes containing copper(I) and silver(I)
is a very interesting area, in view of formation of unusual
metal clusters and multidirectional networks, some of which
display conducting properties.7
four Cu atoms are coordinated to four terminally bonded m-tolyl3P
ligands, two Cu atoms are bonded to two CH CN ligands, and
3
iodide ligands have µ2-I, µ3-I, and µ4-I bonding modes. This
compound has four CuI3P and two CuI3N cores, and geometry
around each Cu center is distorted tetrahedral.The polarizable
iodide ligand and the position of the methyl group in the phenyl
ring attached to the P atom appear to have played the pivotal
role in the formation of monomeric bicapped adamantoid geometry,
which is unique in copper chemistry.
In this Communication, we report an unprecedented
bicapped adamantoid copper(I) cluster, [Cu6(µ2-I)(µ3-I)4(µ4-
I)(m-tolyl3P)4(CH3CN)2] (1), obtained by the reaction of
copper(I) iodide with tri-m-tolylphosphine in acetonitrile. The
reaction of tri-m-tolylphosphine (m-tolyl3P) with copper(I)
iodide in acetonitrile solvent yielded an intriguing product
with empirical composition Cu3I3(m-tolyl3P)2(CH3CN) (A).
The X-ray crystal determination of compound A has shown
that it exists as [Cu6(µ2-I)(µ3-I)4(µ4-I)(m-tolyl3P)4(CH3CN)2]
(1), with a bicapped adamantoid structure (Figure 1).8,9 The
Organophosphorus compounds, such as tertiary phosphines
(PR3), phosphole (DMPP), and bis(diphenylphosphino)-
methane (dppm), react with copper(I) halides to form
tetranuclear complexes of stoichiometry [(PR3)CuX]4 {PR3
) PPh3, X ) Cl (2),1a Br (3),1b I (4);1c PR3 ) PEt3, X ) Cl
(5),2a Br (6),2a I (7);2b PR3 ) PMePh2, X ) I (8),2c PR3 )
t-Bu3P, X ) Br (9)2d}, [(DMPP)CuI]4 (10),3 and [(dppm)2-
Cu4I4] (11).4
Compounds 2 and 5-10 have cubane structure, while 3,
4, and 11 have steplike structure. The solvated compound
[(PPh3)CuBr]4‚2CHCl3 (12) also has steplike structure.1c
(5) Lobana, T. S.; Sharma, R.; Bermejo, E.; Castineiras, A. Inorg. Chem.
2003, 42, 7728-7730.
(6) Lobana, T. S.; Rimple; Castineiras, A.; Turner, P. Inorg. Chem. 2003
, 42, 4731-4737.
* To whom correspondence should be addressed. E-mail: tarlokslobana@
yahoo.co.in. Fax: +91-183-2-258820.
(7) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T. AdV. Inorg. Chem. 1999,
46, 174-303.
† Guru Nanak Dev University.
‡ Osaka City University.
(8) Synthesis of 1: A solution of tri-m-tolylphosphine (0.040 g, 0.13 mmol)
in dry acetonitrile (20 mL) was added to a solution of copper(I) iodide
(0.025 g, 0.13 mmol) in 10 mL of dry acetonitrile, and the mixture
was stirred for 6 h and filtered. Colorless crystals of 1 were obtained
by slow evaporation at room temperature in a few days. Mp: 180-
190 °C. Anal. Calcd for C88H90Cu6I6N2P4: C, 43.40; H, 3.48; N, 1.15.
Found: C, 43.16; H, 3.68; N, 0.90.
(1) (a) Churchill, M. R.; Kalra, K. L. Inorg. Chem. 1974, 13, 1065-
1071. (b) Churchill, M. R.; Kalra, K. L. Inorg. Chem. 1974, 13, 1427-
1434. (c) Churchill, M. R.; DeBoer, B. G.; Donovan, D. J. Inorg.
Chem. 1975, 14, 617-623. (d) Dyason, J. C.; Healy, P. C., Engelhardt,
L. M.; Pakawatchai, C.; Patrick, V. A.; Raston, C. L.; White, A. H. J.
Chem. Soc., Dalton Trans. 1985, 831-838.
(2) (a) Churchill, M. R.; DeBoer, B. G.; Mendak, S. J. Inorg. Chem. 1975,
14, 2041-2047. (b) Churchill, M. R.; Kalra, K. L. Inorg. Chem. 1974,
13, 1899-1904. (c) Churchill, M. R.; Rotella, F. J. Inorg. Chem. 1977,
16, 3267-3273. (d) Goel, R. G.; Beauchamp, A. L. Inorg. Chem. 1983,
22, 395-400.
(3) Attar, S.; Bowmaker, G. A.; Alcock, N. W.; Frye, J. S.; Berden, W.
H.; Nelson, J. H. Inorg. Chem. 1991, 30, 4743-4753.
(4) Marsich, M.; Nardin, G.; Randaccio, L. J. Am. Chem. Soc. 1973, 95,
4053-4054.
(9) Crystallographic data for 1: C88H90Cu6I6N2P4, M ) 2442.29, F-
centered cubic, a ) 26.3990(7) Å, R ) â ) γ ) 90°, V ) 18397.7(8)
Å3, T ) 193.0 K, space group cubic Fd3h (No. 203), Fcalcd ) 1.759 g
cm-3, Z ) 8, µ(Mo KR) ) 3.488 mm-1, 44553 reflections measured
on a Rigaku/MSC Mercury CCD 1000 diffractometer, unique 29636
(Rint ) 0.048). The final R1 was 0.023 for 13831 reflections [I > 2.0σ-
(I)], and wR2 was 0.067 (all data). 1H and 31P NMR spectra were
recorded in CDCl3 at 300.40 and 121.50 MHz frequencies on a FT-
NMR AL-300 MHz JEOL spectrometer.
3766 Inorganic Chemistry, Vol. 43, No. 13, 2004
10.1021/ic049903+ CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/04/2004

COMMUNICATION
compounds, with variable nuclearities of copper and different
bonding modes of iodide ligands (cf. 1, 16, 17). The
formation of monomeric bicapped adamantoid geometry is
the first example in copper chemistry. It is also a rare cluster
compound among other metal complexes.1-7,12 The formation
of adamantoid cluster 1 is the consequence of the m-methyl
group in the phenyl ring which alters the Lewis basicity of
the tri-m-tolylphosphine ligand and the bridging properties
of the iodide ligand. The investigations demonstrate the role
of substituents in an aryl ring coupled with the effect of an
anion in a coordinating solvent like acetonitrile.
It may be interesting to compare the formation of 1 with
the analogous structures reported in the literature. If we
remove Cu(2) and Cu(2c) atoms from compound 1, along
with the CH3CN and m-tolyl3P ligands, the species [Cu4I6]2-
will be formed with adamantane structure, formed by the
three six-membered rings (Figure 2). The dianion of
[MePh3P]2[Cu4I6] (14) has adamantane geometry, similar to
that of 1, but without Cu(2), Cu(2c) atoms and other ligands
(Figure 2).13 Alternatively, one can imagine the formation
of 1 from 14 by coordinating each Cu center to four neutral
m-tolyl3P ligands, and replacing MePh3P+ cations by two
Cu(CH3CN)+ species, which cap two adamantane faces, via
coordination to iodide ligands, as shown in Figure 1.
Similarly, the removal of the Cu(2) atom, along with all the
phosphine ligands, from cluster 1 shall form the species
[Cu5I6(CH3CN)2]-, the same as that in [Cs(18c6)2][Cu5I6(CH3-
CN)2]14 (15). In the anion [Cu5I6(CH3CN)2]-, the CH3CN
ligands are coordinated to Cu(1) and Cu(2c) in 1.
It may be mentioned here that the related isomeric
phosphines, namely, tri-o-tolylphosphine (o-tolyl3P) and tri-
p-tolylphosphine (p-tolyl3P), with copper(I) iodide, formed
an iodo-bridged dimer [Cu2(µ2-I)2(o-tolyl3P)2] (16), similar
to literature reports, [Cu2(µ2-I)2(o-tolyl3P)2]‚toluene, [Cu2-
(µ2-I)2(o-tolyl3P)2(CH3CN)2]‚ CH3CN,15 or cubane, [Cu4(µ3-
I)4(p-tolyl3P)4] (17), similar to 2 and 5-10 as discussed
above.
Figure 1. Structure of bicapped adamantoid cluster 1 without m-tolyl and
CH3 groups.
Figure 2. Structure of bicapped adamantoid cluster 1 without Cu(2) and
Cu(2c) atoms and other ligands.
Cu(2) and Cu(2c) atoms are the capping atoms to which CH3-
CN ligands are bonded.9 Each ring of adamantane is formed
by three Cu and three bridging iodide ligands. Two Cu(2)-
NCMe moieties are disordered into four positions, and the
Cu(2) atoms occupy two of four Cu3I3 faces of the adaman-
tane framework Cu4I6 (Figure 2) of cluster 1.
Cluster 1 has one (µ2-I), four (µ3-I), and one (µ4-I) bonding
modes of iodide ligands {Cu-I ) 2.584(1) Å, 2.690(1) Å},
with terminal bonding by m-tolyl3P {Cu-P ) 2.257(1) Å}
and CH3CN {Cu-N ) 2.077(5) Å} ligands, and these bond
distances are similar to literature reports.10,11 The geometry
around each Cu center is distorted tetrahedral with bond
angles in the range 102-116°. The proton NMR spectrum
of cluster 1 in CDCl3 has shown the methyl protons of the
aryl ring at δ )2.21 ppm and those of CH3CN at 2.02 ppm.
Aryl ring protons absorbed at δ ) 7.59m (6H, o-CH), 7.31m
(3H, p-CH), and 7.15m (3H, m-CH). The 31P NMR spectrum
of this cluster in CDCl3 solvent has shown one peak at δ )
Acknowledgment. One of us (P.K.) is thankful to Guru
Nanak Dev University for research facilities. Financial
support from Council of Scientific and Industrial Research,
New Delhi, is gratefully acknowledged.
Supporting Information Available: X-ray crystal data in CIF
format. This material is available free of charge via the Internet at
http://pubs.acs.org. The CCDC number for this CIF is 229703.
17.6 ppm, with a coordination shift of δcomplex - δligand
)
IC049903+
24.2 ppm.10,11
The polarizable iodide ligand and the position of the
methyl group in the phenyl ring attached to the P atom appear
to have played the pivotal role in the formation of copper(I)
(12) (a) Batten, S. R.; Harris, A. R.; Jensen, P.; Murray, K. S.; Ziebell, A.
Dalton 2000, 3829-3835. (b) Leonard, R. M.; Subramanian, S.;
Zaworotko, M. J. J. Chem. Soc., Chem. Commun. 1994, 1325-1326.
(13) Bowmaker, G. A.; Clark, G. R.; Paul Yuen, D. K. J. Chem. Soc.,
Dalton Trans. 1976, 2329-2334.
(10) (a) Lobana, T. S.; Castineiras, A. Polyhedron 2002, 21, 1603-1611
and references therein. (b) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A.
J. Org. Chem. 1997, 62, 7512.
(11) Lobana, T. S.; Paul, Seema; Castineiras, A. Polyhedron 1997, 16,
4023-4031.
(14) Domasevitch, K. V.; Rusanova, J. A.; Vassilyeva, O. Y.; Kokozay,
V. N.; Squattrito, P. J.; Sieler, J.; Raithby, P. R. J. Chem. Soc., Dalton
Trans. 1999, 3087-3093.
(15) Bowmaker, G. A.; Hanna, J. V.; Hart, R. D.; Healy, P. C.; White, A.
H. Aust. J. Chem. 1994, 47, 25-45.
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