Copper mixed-metal clusters

Bruce and co-workers (2, 3) prepared several mixed-metal clusters that contain copper. Unlike most of the compounds discussed in this review, these particular mixed-metal clusters possess acetylides as ligands instead of carbon monoxide. Ir2Cu4(PPh3)2(Cs Ph)8 (13) (3, 45) results from the reaction shown in Eq. (56). 

Melnik and Parish (10) correlated 197Au Mossbauer and X-ray structural data for gold clusters in 1986, and Salter (11) has recently published a review of the stereochemical nonrigidity exhibited in solution by the metal skeletons of some mixed-metal clusters containing copper, silver, and gold. 

Thiometallates (8) and Ta6Sn " serve as synthons, for instance, for the preparation of mixed-metal clusters involving iron or copper and silver, respectively. The discrete polynuclear TasSi/" and Nb4Se22 anions, prepared by traditional solid-state routes, have a structure related to that of polynuclear Mo oxysulfide anions. Nb-Cu chalcogenido clusters stabilized by phosphines could be prepared directly from NbCls (equation 8). The anion (9), for instance, is based on two CusNbSsCl heterocubane units linked by three /u.3-chlorine. ... 

Table 12. Emission Data for Copper and Mixed-Metal Clusters...

Amoroso AJ, Lewis J et al (1993) Mixed-metal clusters containing osmium and gold. In Welch AJ, Chapman SK (eds) The chemistry of the copper and zinc triads, 1st edn. Royal Society of Chemistry, Cambridge... 

In the extreme class III behaviour,360-362 two types of structures were envisaged clusters and infinite lattices (Table 17). The latter, class IIIB behaviour, has been known for a number of years in the nonstoichiometric sulfides of copper (see ref. 10, p. 1142), and particularly in the double layer structure of K[Cu4S3],382 which exhibits the electrical conductivity and the reflectivity typical of a metal. The former, class IIIA behaviour, was looked for in the polynuclear clusters of copper(I) Cu gX, species, especially where X = sulfur, but no mixed valence copper(I)/(II) clusters with class IIIA behaviour have been identified to date. Mixed valence copper(I)/(II) complexes of class II behaviour (Table 17) have properties intermediate between those of class I and class III. The local copper(I)/(II) stereochemistry is well defined and the same for all Cu atoms present, and the single odd electron is associated with both Cu atoms, i.e. delocalized between them, but will have a normal spin-only magnetic moment. The complexes will be semiconductors and the d-d spectra of the odd electron will involve a near normal copper(II)-type spectrum (see Section 53.4.4.5), but in addition a unique band may be observed associated with an intervalence CuVCu11 charge transfer band (IVTC) (Table 19). While these requirements are fairly clear,360,362 their realization for specific systems is not so clearly established. 

Other metallic clusters that have been demonstrated to show the QDL effect are palladium [116, 117], silver [118] and copper [119]. Palladium MFCs capped with mixed monolayers of hexanethiolate/dodecanethiolate and ferrocene thiolate ligands are prepared in a manner similar to that employed for gold MFCs. The DPV studies exhibit a quantized charging effect but the current peaks are not as well defined as those observed for Au-MPCs. Capacitance values of the order of 0.35 aF are obtained, indicating smaller core sizes or thicker monolayer dielectrics [116]. 

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