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DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, 2969–2972 2969 Syntheses and structures of new copper(I) selenide clusters [Cu32Se16(PPh3)12], [Cu52Se26(PPh3)16] and [Cu72Se36(PPh3)20] † Andreas Eichhöfer and Dieter Fenske * Institut für Anorganische Chemie, Universität Karlsruhe, Engesserstraße Geb. Nr. 30.45, D-76128 Karlsruhe, Germany Received 15th May 1998, Accepted 20th July 1998 The reaction of Se(SiMe3)2 with copper(I) acetate in the presence of PPh3 yielded the new clusters [Cu32Se16(PPh3)12] 2, [Cu52Se26(PPh3)16] 3 and [Cu72Se36(PPh3)20] 4 depending on the conditions.The molecular structures of 2, 3 and 4 have been characterised by X-ray crystallography and compared with the known cluster [Cu146Se73(PPh3)30] 1 obtained from the same reaction under diVerent conditions. Introduction The synthesis of large metal-containing clusters is of considerable interest because these compounds are good model systems for investigating the chemical and physical properties of solid state materials. This is particularly important for nanoparticulate binary metal chacogenides which show quantum eVects such as size-dependent band gaps.1 We have been successful in preparing a large number of copper selenide clusters using the reaction of CuX (X = Cl or OAc) with Se(SiMe3)2 and PR3 (R = organic group) outlined in eqn.(1). Some of the compounds we have structurally charac- 2CuX1yPR31Se(SiMe3)2 THF or Et2O 22SiMe3X [Cu2Se(PR3)y]n (1) terised are as follows: [Cu12Se6(PnPr3)8], [Cu26Se13(PEt2Ph)14], [Cu30Se15(PiPr3)12], [Cu36Se18(PtBu3)12], [Cu44Se22(PEt2Ph)18] and [Cu70Se35(PEt3)22].A noteworthy example is the structure of [Cu146Se73(PPh3)30] 1 one of the largest known structurally characterised clusters.2b From the range of products listed above it can clearly be seen that the phosphine has a profound role in determining the size of the copper selenide cluster. This may be attributed both to steric eVects due to the characteristic Tolman cone angle and to kinetic factors arising from stabilisation of copper/phosphine/ acetate clusters.We now wish to report that other factors such as ligand concentration, temperature and solvent also influence cluster formation. For this study we have conducted a detailed investigation of the CuOAc/Se(SiMe3)2/PPh3 system from which we have previously isolated 1. Experimental Standard Schlenk techniques were employed throughout the syntheses using a double-manifold vacuum line with high purity dry nitrogen.The solvents diethyl ether, tetrahydrofuran and diglyme were dried over sodium–benzophenone and distilled under nitrogen. CuOAc3 and Se(SiMe3)2 4 were prepared according to standard literature procedures. Syntheses [Cu32Se16(PPh3)12] 2. PPh3 (1.73 g, 6.6 mmol) was added to a suspension of copper(I) acetate (0.27 g, 2.2 mmol) in THF (40 † Dedicated to Professor Brian F. G. Johnson on the occasion of his 60th birthday.mL). A clear colourless solution was formed. Upon the addition of Se(SiMe3)2 (0.25 mL, 1.1 mmol) the solution gradually turned yellow, and subsequently dark brown. After 1 d, 20 mL of diethyl ether were added to a solution cooled to 4 8C. After 3 d at this temperature, dark yellow crystalline plates of 2 were formed. Yield: 54% (Found: C, 39.02; H, 2.90. C216H180Cu32- P12Se16 requires C, 40.26; H, 2.80%). [Cu52Se26(PPh3)16] 3. PPh3 (1.73 g, 6.6 mmol) was added to a suspension of copper(I) acetate (0.27 g, 2.2 mmol) in THF (40 mL).A clear colourless solution was formed. Upon addition of Se(SiMe3)2 (0.25 mL, 1.1 mmol), the solution gradually turned yellow, and subsequently dark brown. After 1 d, 20 mL of diethyl ether were added and the solution was kept at room temperature. After 2 d, dark yellow crystalline plates of 2 were formed in low yield, and after 2 additional days, black crystals of 3 began to grow as the major product of the reaction.Yield: 50% (Found: C, 37.1; H, 2.80. C288H240Cu52P16Se26 requires C, 36.2; H, 2.5%). [Cu72Se32(PPh3)20] 4. PPh3 (1.28 g, 4.9 mmol) was added to a suspension of copper(I) acetate (0.20 g, 1.63 mmol) i

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