Recent development of linearly ordered multinuclear transition-metal complexes

This paper reviews the recent development of linearly ordered multinuclear transition-metal complexes, which have been of increasing interest as potential nanostructured molecular units and their precursors. In particular, it focuses on our recent results of platinum-based homo- and heteromultimetallic complexes supported by the tridentate phosphine ligands, bis(diphenylphosphinomethyl)phenylphosphine (dpmp). The synthetic strategy involved the metal core expansion using the diplatinum precursors having two uncoordinated phosphine pendants, syn- and anti-[Pt-2(mu-dpmp)(2)(RNC)(2)](2+) (11 and 12), which allowed us to gain access to versatile homo- and heterotrinuclear complexes with Pt2M cores. Reactions of 11 with d(10) and d(8) metal fragments afforded the Pt-Pt-M metal frameworks (M = Pt, Pd, Au, Ag, Cu, Ir, Rh), and in contrast, those of 12 gave the Pt-M-Pt ones (M = Pt, Pd, Rh). The inserted position of the additional metal interestingly depends on the two dpmp arrangement of the starting diplatinum complexes. The corresponding chemistry of palladium and gold complexes is also described. Since the metal-metal bonded triplatinum complex, linear-[Pt-3(mu-dpmp)(2)(RNC)(2)](PF6)(2) (16), was regarded as a minimal model for the surface of metal catalysts, its reactions with various small organic molecules were examined. Further, the axial ligand exchange reactions of 16 with bulky aromatic bisisocyanide led to a one-dimensional assemblage of the linear Pt3 units, resulting in rigid rod-like cluster polymers, and the reduction of 16 afforded the linearly ordered hexaplatinum cluster molecules supported by four dpmp ligands through a direct combination of the two linear Pt-3 fragments.