For the last few years we have been working on the synthesis and characterization of metal-chalcogenide clusters. For most of the transition metals, one observes the formation of relatively low-nuclearity cluster complexes, [1] such as [Co 6 E 8 -(PR 3 ) 6 ] (E = S, Se, Te; R = organic groups) und [Ni 34 Se 22 -(PPh 3 ) 20 ]. In contrast, for clusters of copper and silver one can find a rich variety of structures. [2] Recently, we reported the synthesis of metal-rich silverchalcogenide clusters, such as [Ag 70 S 20 (SPh) 96 ] (dppm = bis(diphenylphosphanyl)methane; dppb = 1,4-bis(diphenylphosphanyl)butane), particles with diameters in the nanometer range. The surfaces of these clusters are protected by ligands, thus preventing further reaction to form the thermodynamically stable binary silver chalcogenide salts.[3] Perhaps surprisingly, these cluster complexes could be prepared reproducibly and in high yield by the reaction at room temperature of, for example, silver carboxylates with S(tBu)SiMe 3 in the presence of tertiary phosphanes. In contrast, at higher temperatures amorphous Ag 2 S was formed. We therefore propose that these metal-rich clusters represent intermediates in the formation of solid Ag 2 S. When the progress of the reaction is monitored by dynamic light scattering, initially no particles are formed that are large enough to be observed by this technique. However, after several days particles form in the size range 2-4 nm and crystallize out of solution. The structural determinations of these large clusters proved problematic. With nuclearities of up to 100 metal atoms, crystals generally diffract well to up high 2q values (50-608 with Mo Ka ); the atoms have low temperature factors, and no high residual electron density is observed within the clusters. However, this situation changes for larger clusters with nuclearities greater than around 120 metal atoms. For such clusters, the intensities of the reflections drop off rather sharply above 2q % 408, and the structure refinement results in unsatisfactorily high R factors, with high residual electron density within the cluster molecule. Satisfactory R factors can only be obtained if this electron density can be modeled during the refinement. As this electron density generally lies close to the heavy atoms, it can be difficult to interpret and thus complicates efforts to give precise estimates of the molecular formulae. These effects may result from a range of factors: 1) There is no perfect translational order in the lattice. 2) With the silver-chalcogenide clusters there is a tendency towards nonstoichiometry, as is seen for the binary phases. [4] This behavior could be a consequence of the rather similar electronegativities of silver and the chalcogenides. There is no clear distinction between Ag + and E 2À(E = S, Se, Te), and the clusters behave rather like alloys. [5] 3) The surface tension of the spherical molecules generates a Laplace pressure within the molecule, which can result in a disorder or even a phase transition. 4) Interacti...

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Dedicated to Professor Hans Bock on the occasion of his 75th birthday Numerous reports have described the syntheses and structures of metal-rich compounds. In recent years, research activities in this field have been very successful, especially in the synthesis of heteropolyacids and clusters of maingroup and transition-metal elements. 20 ]. [1][2][3] Another area of interest is the preparation of metal chalcogenide clusters.[4] Recently, the synthesis and crystal structure of an ionic compound containing the anion [Cd 16 In 64 S 134 ] 44À was reported.[5] The size of this structure is within the order of magnitude of nanocrystalline materials.Metal-rich complexes are also known from chalcogenides of other electron-rich transition-metal elements. [6] and other Cu and Ag chalcogenide clusters that were synthesized by using tertiary phosphanes to inhibit the competing formation of the thermodynamically preferred binary metal-chalcogenide phases. Quantum chemical investigations showed that clusters of this type are metastable compounds whose collapse is kinetically prevented. [7] There is some evidence that selenide and telluride clusters, such as [Cu 146 [15] These compounds form in high yields upon

Dedicated to Professor Achim M¸ller on the occasion of his 65th birthday Many investigations towards synthesis and structural characterization of large metal-rich clusters have been reported over the last few years. Particularly noteworthy are the oxometallates of molybdenum described by M¸ller et al.; only recently Na 48 [H x Mo 368 O 1032 (H 2 O) 240 (SO 4 ) 48 ]¥n 1000 H 2 O (x % 16; n % 1000), the largest known derivative of a heteropolyacid was structurally characterized. [1] Other examples of large cluster complexes are [Pd 145 (CO) x (PEt 3 ) 30 ] (x % 60) made by Dahl et al. [2] and [Ga 84 {N(SiMe 3 ) 2 } 20 Li 6 Br 2 (thf) 20 ] reported by Schnˆckel and Schnepf. [3] The synthesis of the larger Ag±S cluster complexes [Ag 14 S(SPh) 12 (PPh 3 ) 8 ] [4] and [HNEt 3 ] 4 -[Ag 50 S 7 (SC 6 H 4 tBu) 40 ] [5] was recently achieved by Jin et al.Over the last few years one of our major fields of interest was the synthesis of transition-metal clusters containing S, Se, Te, P, As, and Sb as bridging ligands, for example, copperchalcogenide clusters stabilized by tertiary phosphane ligands. [6] Reactions of transition-metal salts with Group 16 silyl derivatives E(SiMe 3 ) 2 or RESiMe 3 (R ¼ alkyl-or aryl-; E ¼ S, Se, Te) allows access to these clusters. [7] Addition of tertiary phosphanes to these reactions prevents the formation of the thermodynamically stable binary phase. [8] Compounds obtained by this route include: [Cu 146 Se 73 -(PPh 3 ) 30 ], [9] [Ag 172 Se 40 (SenBu) 92 (dppp) 4 ] [10] [Ag 38 Te 13 (TetBu) 12 (dppe) 6 ] (dppe ¼ bis(1,2-diphenylphosphanyl)ethane), [11] [Au 18 Se 8 -(dppe) 6 ]Cl 2 [12] , and [Zn 16 Te 13 (TePh) 6 (tmeda) 5 ] [13] (tmeda ¼ tetramethylethylenediamine). Herein we report the synthesis of the Ag±S clusters 1, 2, and 3 containing 120 and 282 heavy atoms, respectively, in the cluster core. ½Ag 70 S 16 ðSPhÞ 34 ðPhCO 2 Þ 4 ðtriphosÞ 4 1 ½Ag 188 S 94 ðPnPr 3 Þ 30 2 ½Ag 188 S 94 ðPnBu 3 Þ 30 3The reaction of a suspension of silver benzoate and triphos [1,1,1-tris{(diphenylphosphanyl)methyl}ethane] with a mixture of S(Ph)SiMe 3 and S(SiMe 3 ) 2 (2:1) at À20 8C in diglyme produces a deep red solution from which small red needles of 1 [Eq. (1)], can be isolated.Reaction of S(SiMe 3 ) 2 with silver trifluoroacetate and PnPr 3 at À40 8C in diglyme initially produces a red solution. After a few hours stirring, the reaction is allowed to warm up to room temperature. The solution becomes dark and black crystals of 2 are formed [Eq. (2)]. Employment of PnBu 3 in an analogous reaction produces black crystals of 3 [Eq. (2)]. Depending on the reaction conditions, 2 is often produced together with black amorphous Ag 2 S. Attempts to recrystallize 2 and 3 from THF or CH 2 Cl 2 failed and produced Ag 2 S as the only isolatable material. The different colors of 1 and 2 (red and black) arise from quantum size effect, which result from the dependency of the band gap on particle size. [14] 2 þSðSiMe3 Þ2 þPnPr3The molecular structures of complexes 1 and 2 in the solidstate were determined by X-ray crysta...

A Pd20 polyhedron all of whose surfaces are bridged by μ5‐As atoms is one distinctive feature of 1, the title compound with the highest Pd content. Compound 1 was obtained upon treatment of [PdCl2(PPh3)2] with As(SiMe3)3. Other products of the reaction were the Pd2 and Pd9 complexes mentioned in the title as well, whereby the Pd9 complex also results from the reaction of [Pd3S2Cl2(PPh3)4] with As(SiMe3)3.