metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
exists in the CuÐS distances; the CuÐS1 distance of
Ê
2.376 (1) A is shorter than the corresponding CuÐS2 distance
Ê
of 2.467 (1) A. This difference indicates that different forms of
Communications
ISSN 0108-2701
the ligand exist, i.e. L and LH, with the ligand containing S1
functioning as a thiolate. Further support for this assignment is
(Benzoxazole-2-thiolato-S)(benz-
oxazole-2-thione-S)bis(triphenylphos-
phine)copper(I)
T. Nakahodo,a E. Horna,b and E. R. T. Tiekinkc*
aDepartment of Chemistry, Rikkyo University, Nishi-Ikebukuro, Tokyo 171-8501,
Japan, bTsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba,
Ibaraki 305-8577, Japan, and cDepartment of Chemistry, The University of Adelaide,
Adelaide 5005, Australia
found in the magnitude of the associated CÐS distances, with
Ê
C1ÐS1 of 1.701 (2) A being signi®cantly longer than C8ÐS2
Ê
of 1.672 (3) A. The C8ÐS2 distance in the complex is, as
Correspondence e-mail: edward.tiekink@adelaide.edu.au
Ê
expected, longer than the comparable distance of 1.643 (3) A
Received 3 August 2000
Accepted 21 August 2000
in the structure of LH (Groth, 1973). The H2 atom, i.e. bound
to N2, was located from a difference map (see Experimental),
suggesting ordering of this atom. Further, this is consistent
with the ligand containing the S2 atom functioning primarily
as a thione and thus it should be formulated as LH.
The H2 atom participates in an interesting intramolecular
interaction in that it forms a close contact with the N1 atom, as
shown in Fig. 1. While both ligands are effectively planar, that
The Cu atom in [Cu(C7H4NOS)(C7H5NOS)(C18H15P)2] is
tetrahedrally coordinated by a P2S2 donor set. One S atom is
derived from neutral benzoxazole-2-thione and the other from
the deprotonated form of the ligand. The two sulfur ligands
are connected via an NÐHÁ Á ÁN interaction, leading to the
formation of an eight-membered ring.
Ê
containing the S1 atom has a mean deviation of 0.015 A and
the LH ligand, i.e. with formally sp3 N, is less planar with a
Comment
Ê
mean deviation of 0.035 A. The L and LH ligands are disposed
Metal±phosphine complexes are ubiquitous in coordination
chemistry owing to their wide variety of applications, such as
in catalysis, biological chemistry and simply as stabilizing
ligands. In a biological context, the mononuclear gold complex
(1-thio-ꢀ-d-glucopyranose-2,3,4,6-tetraacetato-S)(triethyl-
phine)gold(I), aurano®n, is used in the treatment of rheu-
matoid arthritis (Sadler & Sue, 1994). Subsequently, other
phosphine±gold(I) thiolates have been tested for antiarthritic
activity (Whitehouse et al., 1998), as well as for cytotoxicity
(Webster et al., 1996). Research in this ®eld has been directed
towards coupling phosphine±gold(I) centres with thiol ligands
that have biological activity in their own right (Cookson et al.,
1994). The thiol benzoxazole-2-thione, LH, is a precursor to
compounds that are known to possess antifungicidal activity.
Recently, some organotin derivatives were evaluated for their
trypanocidal activity, i.e. activity against the parasite that
causes sleeping sickness (Susperregui et al., 1998). In this
report, the structure of a phosphine±CuI complex is reported
containing this thiol, (I).
The molecular structure of (I) is shown in Fig. 1 and
selected geometric parameters are listed in Table 1. The Cu
atom exists within a P2S2 donor set de®ned by two phosphine
P atoms and two S atoms. One S atom is derived from a
deprotonated ligand whilst the other is from the neutral form,
so that the Cu atom is in the +1 oxidation state. The overall
coordination geometry is distorted tetrahedral, with the widest
angle at Cu involving the two bulky phosphine ligands. The
CuÐP distances are experimentally equivalent, but a disparity
so as to be almost orthogonal to each other, so that the
dihedral angle between their respective least-squares planes is
67.9ꢁ. The respective N2ÐH2, H2Á Á ÁN1 and N2Á Á ÁN1
Ê
distances are 0.95, 1.78 and 2.662 (3) A, and the angle
subtended at H2 is 154ꢁ. This mode of intramolecular asso-
ciation between L and LH leads to the formation of an eight-
membered ring. Other intramolecular interactions serve to
stabilize the molecular structure. Thus, there are face-to-face
ꢁÁ Á Áꢁ interactions between L and the C15±C20 aromatic ring
although, owing to the mismatch in sizes, the overlap is such as
to place the ®ve-membered ring of L in closer proximity to the
adjacent aromatic ring. The distance between the centroid of
Ê
the ®ve-membered ꢁ ring and that of C15±C20 is 3.80 A
Ê
(dihedral angle 14.6 ). A comparable separation of 4.27 A is
noted between the ®ve-membered ring of LH and C39±C44;
dihedral angle 4.1ꢁ. Furthermore, intramolecular SÁ Á ÁH
Ê
Ê
Ê
(S1Á Á ÁH40 2.78 A and S2Á Á ÁH46 2.82 A) and O1Á Á ÁH
(O1Á Á ÁH22 2.48 A) contacts are also observed, precluding
their participation in intermolecular interactions (see below).
An analogous association between the N atoms of L and LH,
as described above, has been reported previously.
In the structure of [(Ph3P)2CuL2][Li(thf)2]Á0.5THF, the
[Li(thf)2]+ cation substitutes for the H+ in (Ph3P)2Cu(L)(LH)
(Beswick et al., 1996). In this structure, both molecules
comprising the asymmetric unit have crystallographically
imposed twofold symmetry, indicating that within each inde-
pendent molecule the two CuÐS distances are equal. This
ꢀ
1316 # 2000 International Union of Crystallography Printed in Great Britain ± all rights reserved
Acta Cryst. (2000). C56, 1316±1318
Nakahodo
