Group 9 and 10 Carbonyl Clusters

The chemistry of carbonyl clusters of group 9 and 10 metals presented in this chapter aims to cover the scientific literature within this field that has been published from 2006 onwards, as the preceding years are reported in COMC III. This chapter focuses on the latest findings regarding heteroleptic and homoleptic species with a nuclearity of four or more metal atoms. The chapter is divided in separated sections, one for each metal, and in sub-sections gathering the reported compounds in categories, hopefully making them easier to find for the reader. “Heterometallic species” refer to compounds of the main group 9 or 10 metals together with either other transition or with post-transition metals. Conversely, in the sub-sections stating “containing post-transition metals” we intend clusters of the specific element where post-transition metals are actually contained inside the metal cluster frame. Nonetheless, in some cases the two sub-categories are entangled. The same logic has been applied when considering clusters containing main-group elements, that is elements belonging to either the 2nd or 3rd row of the periodic table. As the structural aspects are crucial, we reported various crystal structures of selected compounds.1 The chemistry of metal carbonyl clusters started with the pioneering work of Walter Otto Hieber, and it highly developed in the 1970s and 1980s especially thanks to the systematic studies of the research groups of Brian F. G. Johnson and Lord Jack Lewis in Cambridge, Paolo Chini in Milan and, later, his pupil Giuliano Longoni, who after the premature demise of Chini continued his studies in Bologna. The concurrent improvement of crystallographic diffractometers was essential, as they allowed to determine the molecular structures of the isolated compounds that, owing to their dimensions, were very challenging for the existing techniques. Among the many crystallographers that worked in the field we cannot fail to mention Lawrence F. Dahl, who recently passed away. Together with the late Paolo Chini, the world of metal clusters, especially of high nuclearity, has lost another one of its more esteemed representatives. After a decrease of interest in the 1990s, cluster chemistry gained a renewed attention in the 2000s, also due to the outbreak of nanotechnology, and the realization that large molecular carbonyl clusters are, in the end, metal nanoparticles stabilized by CO ligands with the advantage of being atomically precise.