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Encyclopedia of Physical Science and Technology EN010H-470 July 16, 2001 16:53

306 Nanosized Inorganic Clusters

1. organic solvent
X = Cl, OAc
2. +E(SiMe 3 ) 2

CuX + PR 2 R −−−−−−→ [Cu 2n E n (PR R ) m ]R, R = org. group

2
−SiMe 3 X E = S, Se
SCHEME 1 General route to the preparaton of metal chalcogenides.

FIGURE 3 Structure of the Se network in [Cu 146 Se 73 (PPh 3 ) 30 ].
t
The Se atoms on the first and third layers are shown as empty FIGURE 4 Structure of [Ag 90 Se 38 (Se Bu) 14 (PEt 3 ) 22 ] without C
spheres and those of the middle layer as hatched spheres. atoms. Ag atoms are shown as empty spheres, Se atoms are
depicted as horizontally hatched spheres, and the Se atoms of
t
the Se Bu groups are hatched spheres.
The reaction of AgCl, for example, with Se(SiMe 3 ) 2 in
thepresenceofPR 3 usuallyaffordsinsolubleAg 2 Se,while

the corresponding reaction with R TeSiMe 3 preferably polyhedron, which is built up from Se 3 faces (Fig. 5).
n
provides silver clusters with Te 2− and TeR ligands. The The reaction of Ag(C 11 H 23 CO 2 ) with BuSeSiMe 3 and
−
n
t
t
structures of the compounds formed depend very much P Bu 3 yields [Ag 114 Se 34 (Se Bu) 46 (P Bu 3 ) 14 ] (Fig. 6). If
upon the type of the tertiary phosphane used and also the monodentate phosphane ligands are replaced by

on the organic group R . Examples of related compounds bis(diphenylphosphino) propane (dppp), under the same
n n
◦
with known structures are [Ag 6 (µ 3- Te Bu) 4 (µ-Te Bu) 2 reaction conditions (Scheme 3) (−30 C) the largest
n
(PEt 3 ) 4 ], [Ag 10 (TePh) 10 (PMe 3 ) 2 ] ∞ , [Ag 30 (TePh) 12 Te 9 known Ag cluster [Ag 172 Se 40 (Se Bu) 92 (dppp) 4 ] is formed
n
(PEt 3 ) 12 ],[Ag 32 (µ 3 -Te Bu) 18 Te 7 (PEt 3 ) 6 ], [Ag 46 (TeMes) 12 (Fig. 7).
n
Te 17 (PEt 3 ) 16 ], and [Ag 48 (µ 3 -Te Bu) 24 Te 12 (PEt 3 ) 14 ]. Oth- The layer clusters of the type {Ag 114 } and {Ag 172 } are
er Ag clusters can be isolated from the reaction of sil- structurally different from the aforementioned systems,
ver carboxylates with RSeSiMe 3 (R = organic group) and for instance, from the spherical {Ag 30 } and {Ag 90 } clus-
n
PR 3 or bidentate phosphanes. The reaction of P Pr 3 with ters. There is a remarkable agreement between the Se
t BuSeSiMe 3 and silver benzoate in pentane at −40 C af- skeletons in the {Ag 114 } and {Ag 172 } clusters and that of
◦
t
n
fords [Ag 30 Se 8 (Se Bu) 14 (P Pr 3 ) 8 ] (Scheme 2). Using the Ag 2 Se (Fig. 8). The cluster structures can realistically be
samereactionconditionswithPEt 3 asligands,onlythefor- described as sections of the binary phase Ag 2 Se. With in-
t
mation of [Ag 90 Se 38 (Se Bu) 14 (PEt 3 ) 22 ] can be observed. creasing cluster size, the distribution of the Ag atoms in
However, the {Ag 90 } cluster (Fig. 4) shows no similar- the molecular structure becomes more random. Obviously
ity with the corresponding binary phase Ag 2 Se but excit- there is a tendency to a kind of disordering of the Ag atoms
ing structural details: The Se atoms form a torus-shaped which is also observed in the bulk material Ag 2 Se.
t BuSeSiMe 3 t BuSeSiMe 3
n
t −−−−−−→ t
Ag 90 Se 38 (Se Bu) 14 (PEt 3 ) 22 ←−−−−−− Ag(C 6 H 5 CO 2 ) Ag 30 Se 8 (Se Bu) 14 P Pr 3 8
PEt 3 P n Pr 3
SCHEME 2 Synthetic route to Ag 90 and Ag 30 clusters.