Alkyne-substituted mixed-metal clusters

Most of the reported reactions between tetranuclear clusters and alkynes involve mixed-metal cluster species. In these systems hydride and carbon monoxide substitution generally occurs [Eq. (11)] (194-200), although in some cases Me3NO has been used to activate the starting material (201, 202), and in still others cluster breakdown takes place even under mild reaction conditions (203). Rh4(CO)12 (204) and Ir4(CO)12 (205) retain their nuclearity in reactions with alkynes, but in the latter case the metal framework geometry is altered (Fig. 7). The use of [Ir4(CO)11Br] instead of Ir4(CO)12 in reactions with alkenes produces alkene-substituted tetranuclear complexes (189), as shown in Fig. 7. Few other homonuclear clusters have been found to react with alkynes (206-208). In the reaction between the tetranuclear cluster Cp2W2Ir2(CO) 0 and diphenylacetylene two independent processes... 

Reactions between alkyne-substituted clusters and other metallic species have been used frequently as synthetic routes to mixed-metal clusters, particularly for Ru-Ni (214-217), as exemplified by Eq. (22), and Ru-Fe (220) complexes. In all these reactions the new metallic group forms bonds with the organic unit and with the metallic framework. It is possible that the first step in these reactions is the... 

Direct application of Ru3(CO)i2 in photochemical synthesis has been described in detail [120]. Thermal reactions of this cluster in presence of two-electron donors L affords [Ru3(CO)9L3]. The discovery in 1974 that irradiation of the cluster under those conditions produces mononuclear products instead of the substituted clusters initiated a wealth of research in Ru-clusters as precursors in photochemical synthesis [121]. Much research has been devoted to the preparation of mononuclear f/ -olefin complexes, as well as alkyne complexes. For example, [Ru(CO)3(PPh3)2] has been reported as an active catalyst for olefin polymerisation, and as such, many investigations have dealt with the reactivity of this compound. Other directions of research include formation of metallacycles, generation of new cluster species, and mixed transition metal/non-metal clusters. 

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