stabilize such particles and explains the observation that only amorphous binary
materials are produced in these reactions [58, 59]. What has proven to be remarkably effective, however, is the combination of both PR 3 ligands in conjunction with surface tellurolate groups, RTe
À . Thus the 4:8:1:2 combination of AgCl,
PEt 3 , Te(SiMe 3 ) 2 and PhTeSiMe 3 results in the formation of the cluster [Ag 30 Te 9 Á
(TePh) 12 (PEt 3 ) 12 ] (16, Figure 13.12) [58]. Interestingly, the structurally related copper tellurolate complex [Cu 29 Te 9 (TePh) 12 (PEt 3 ) 8 ]
À has been reported, formed from
the photochemically induced condensation reaction of two smaller clusters [55].
This Cu 29 cluster and complex 16 represent the only examples with such a demonstrated structural relationship in the CuTe and AgTe series.
In 16, the presence of phenyl groups on the twelve tellurium centers of the
cluster framework assists in stabilizing the AgTe core against further (random)
condensation reactions. These PhTe
À groups adopt m 3 - and m 4 -coordination. The
order of addition of the silylated reagents does not affect the yield of product produced. As is the case with phosphine ligands in the Cu 2 E clusters, modification
of the steric and/or electronic properties of the tellurolate groups can also have a
marked impact on the structure of the AgTe cluster cores. Thus an analogous reaction for the synthesis of 16 substituting PhTeSiMe 3 with (mes)TeSiMe 3 (mes ¼
2,4,6-Me 3 C 6 H 2 ) leads to the high yield formation of [Ag 46 Te 17 {Te(mes)} 12 (PEt 3 ) 16 ]
(17, Figure 13.12), a cluster with a 1.6 Â 0.9 Â 0.8 nm
3 AgTe core [58]. The larger
number of interstitial Te
2À ligands in 17 versus 16 results in the formation of the
higher nuclearity complex, although there are structural similarities between the
two with respect to the arrangement of Ag and Te atoms at the cluster surfaces. A
þ1 oxidation state can be assigned to the silver centers in 16 and 17, as it can in all
silver chalcogenide polynuclear complexes accessed to date.
Other nanometer-sized AgTe clusters reported using RTe
À ligands in combination with PEt 3 include [Ag 32 Te 7 (Te
n Bu) 18 (PEt 3 ) 6 ] and [Ag 48 Te 12 (
n BuTe) 24 (PEt 3 ) 14 ]
[60]. The latter represents the largest crystallographically characterized silver–
tellurium cluster reported to date, however, the oblong AgTe core is best described
as consisting of two Ag 24 Te 16 subunits linked with four m 3 -Te
n Bu ligands. A related
‘‘Ag 24 Te 16 ’’ cluster has yet to be reported. The combination of a bidentate phosphine, AgOAc and
t BuTeSiMe 3 leads to the formation of [Ag 38 Te 13 (Te
t Bu) 12 (Ph 2 P Á
(CH 2 ) 2 PPh 2 ) 3 ] [61].
13.3.3
Ag 2 S
The rich chemistry of silver thiolate clusters [62] has most recently been complemented via the successful incorporation of sulfide ligands into a preformed
Ag x (SR) x to yield a nanometer-sized cluster complex [63]. As outlined in the previous sections, the formation of nanometer-sized semiconductor metal-chalcogen
complexes can only be achieved with the delivery of chalcogenide ions (E
2À ) during
cluster formation. This is of course related to the steric requirements of the
chalcogenolate (RE
À ) moieties which are thus restricted to the surfaces of the
polynuclear frameworks. The nanocluster [Ag 50 S 7 (SC 6 H 4
t Bu-4) 40 ]
4À (18, Figure
13.3 Group XI Chalcogenides 433
materials are produced in these reactions [58, 59]. What has proven to be remarkably effective, however, is the combination of both PR 3 ligands in conjunction with surface tellurolate groups, RTe
À . Thus the 4:8:1:2 combination of AgCl,
PEt 3 , Te(SiMe 3 ) 2 and PhTeSiMe 3 results in the formation of the cluster [Ag 30 Te 9 Á
(TePh) 12 (PEt 3 ) 12 ] (16, Figure 13.12) [58]. Interestingly, the structurally related copper tellurolate complex [Cu 29 Te 9 (TePh) 12 (PEt 3 ) 8 ]
À has been reported, formed from
the photochemically induced condensation reaction of two smaller clusters [55].
This Cu 29 cluster and complex 16 represent the only examples with such a demonstrated structural relationship in the CuTe and AgTe series.
In 16, the presence of phenyl groups on the twelve tellurium centers of the
cluster framework assists in stabilizing the AgTe core against further (random)
condensation reactions. These PhTe
À groups adopt m 3 - and m 4 -coordination. The
order of addition of the silylated reagents does not affect the yield of product produced. As is the case with phosphine ligands in the Cu 2 E clusters, modification
of the steric and/or electronic properties of the tellurolate groups can also have a
marked impact on the structure of the AgTe cluster cores. Thus an analogous reaction for the synthesis of 16 substituting PhTeSiMe 3 with (mes)TeSiMe 3 (mes ¼
2,4,6-Me 3 C 6 H 2 ) leads to the high yield formation of [Ag 46 Te 17 {Te(mes)} 12 (PEt 3 ) 16 ]
(17, Figure 13.12), a cluster with a 1.6 Â 0.9 Â 0.8 nm
3 AgTe core [58]. The larger
number of interstitial Te
2À ligands in 17 versus 16 results in the formation of the
higher nuclearity complex, although there are structural similarities between the
two with respect to the arrangement of Ag and Te atoms at the cluster surfaces. A
þ1 oxidation state can be assigned to the silver centers in 16 and 17, as it can in all
silver chalcogenide polynuclear complexes accessed to date.
Other nanometer-sized AgTe clusters reported using RTe
À ligands in combination with PEt 3 include [Ag 32 Te 7 (Te
n Bu) 18 (PEt 3 ) 6 ] and [Ag 48 Te 12 (
n BuTe) 24 (PEt 3 ) 14 ]
[60]. The latter represents the largest crystallographically characterized silver–
tellurium cluster reported to date, however, the oblong AgTe core is best described
as consisting of two Ag 24 Te 16 subunits linked with four m 3 -Te
n Bu ligands. A related
‘‘Ag 24 Te 16 ’’ cluster has yet to be reported. The combination of a bidentate phosphine, AgOAc and
t BuTeSiMe 3 leads to the formation of [Ag 38 Te 13 (Te
t Bu) 12 (Ph 2 P Á
(CH 2 ) 2 PPh 2 ) 3 ] [61].
13.3.3
Ag 2 S
The rich chemistry of silver thiolate clusters [62] has most recently been complemented via the successful incorporation of sulfide ligands into a preformed
Ag x (SR) x to yield a nanometer-sized cluster complex [63]. As outlined in the previous sections, the formation of nanometer-sized semiconductor metal-chalcogen
complexes can only be achieved with the delivery of chalcogenide ions (E
2À ) during
cluster formation. This is of course related to the steric requirements of the
chalcogenolate (RE
À ) moieties which are thus restricted to the surfaces of the
polynuclear frameworks. The nanocluster [Ag 50 S 7 (SC 6 H 4
t Bu-4) 40 ]
4À (18, Figure
13.3 Group XI Chalcogenides 433