“…The crystalline products are often highly sensitive to both air and moisture, but nevertheless a now extensive family of clusters with stoichiometries MPb 9–12 has been synthesized in this way, including [CuPb 9 ] 3– , [NiPb 10 ] 2– , [AgPb 11 ] 3– , [MPb 12 ] n − (M = Au, Ni, Pd, Pt, Co, Rh, Ir, Mn), and [(Cp*Ru)CuPb 11 ] 2– (Figure ). Our understanding of the mechanism of growth of these clusters from smaller component parts remains limited, although a small number of recent studies have begun to address this critical issue using a combination of X-ray crystallography, mass spectrometry, and computational analysis. , In the formation of the group-5 metal clusters [TaGe 8 As 4 ] 3– and [TaGe 8 As 6 ] 3– , for example, fusion of the known tetrahedral [Ge 2 As 2 ] 2– unit with the (unknown) Ta-containing fragments [TaGe 3 ] − and [TaGe 4 As 2 ] − has been shown to provide a viable route to the isolated products …”