Neutral tantalum−carbide clusters, Ta m C n (m = 1−6, n = 1−7), have been formed in a supersonic expansion following the reaction of tantalum and acetylene in a laser ablation source. These clusters have been subjected to multiphoton ionization at 532 and 355 nm and the mass spectra recorded in a reflectron time-of-flight mass spectrometer. The cluster distributions show a drop off after m = 4 suggesting the stabilization of clusters containing four tantalum atoms. We have investigated the structures of these clusters using density functional theory and shown that the smaller clusters tend to form fragments of face-centered cubes, culminating in the formation of a distorted cube of stoichiometry Ta4C4. The structure of Ta4C4 is shown to be a distorted tetrahedron, or “butterfly”, made up of four tantalum atoms with a carbon atom bonded to each face. The theoretical calculations also indicate that clusters containing three tantalum atoms form a triangle and that there is competition for the carbon atoms to bond to either the face or the edge of the tantalum triangle.

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The interaction of the thionucleobase 2-thiouracil with the triethylphosphinegold(I) cation has been examined employing ab initio molecular orbital theory. Deprotonation of 2-thiouracil (2-TUH) and subsequent association with [Et3PAu]+ leads to the formation of [Et3PAu(2-TU  H)]; a comparison of calculated and experimental geometric parameters reveals a high degree of agreement. The interaction of two [Et3PAu]+ cations with twice deprotonated 2-TUH indicates that the most stable dinuclear structure is one where coordination occurs via the sulfur and one of the nitrogen atoms leading to almost linear P−Au−S and P−Au−N arrangements, respectively.