The Preparation of Large Semiconductor Clusters via the Pyrolysis of a Molecular Precursor.

We have succeeded in preparing nanometer-sized clusters of CdSe via the solution-phase thermolysis of the organometallic compound Cd(SePh) sub 2 (Ph = phenyl, C sub 6 H sub 5). This compound is prepared by the reaction of two equivalents of benzeneselenol, PhSeH, and dimethylcadmium with the concomitant elimination of two equivalents of methane. When the preparative reaction is performed in the presence of Et sub 2 PCH sub 2 CH sub 2 PEt sub 2, the substituted complex [Et sub 2 PCH sub 2 CH sub 2 PEt sub 2] [Cd(SePh) sub 2] sub 2 is formed. This latter complex is readily crystallized from pyridine/heptane, and a single-crystal x-ray structural study shows the crystalline complex to actually be a coordination polymer. Thermolysis of either of these organometallic compounds in the solid state gives bulk CdSe in high yield. Thermolysis in 4-ethylpyridine solution gives nanoclusters as shown by electronic spectroscopy and transmission electron microscopy.