Chiral Octapalladium Chains Supported by Enantiopure -Stereogenic Linear Tetraphosphines, ()- and ()-PhPCHP(Ph)CHP(Ph)CHPPh.

Binuclear Pd(II) and Pt(II) complexes supported by -dpmppm (bis[(diphenylphosphinomethyl)phenylphosphino]methane) in a triply-bridged -form, [MCl(-dpmppm)] (M = Pd (), Pt ()), readily reacted with 2,6-xylyl isocyanide (XylNC) in the presence of NHPF to afford MCl(-dpmppm)(XylNC) (M = Pd (), Pt ()), in which each metal center accommodates one isocyanide ligand at the position to the inner P atom of dpmppm. Similarly, treatment of and with axially chiral ()-1,1'-binaphthyl-2,2'-bisisocyanide (-Binac) in the presence of NHOTf gave cyclic tetranuclear complexes, {MCl(-dpmppm)(-Binac)} (M = Pd (), Pt ()), where two {MCl(-dpmppm)} fragments are connected by two -Binac ligands through chirality sorting of ()-dpmppm and ()-Binac. Complex could be transformed into the halide exchanged tetranuclear complexes, {PdX(-dpmppm)(-Binac)} (X = Br (), I ()), to show that the rectangular arrangement of four Pd(II) ions is elongated by repulsive interaction between halide ligands. By using ()- and ()-Binac, enantiopure Pd complexes, {PdCl(()-dpmppm)(()-Binac)} ( and ), were successfully isolated as pure crystalline forms, from which enantiopure ()- and ()-dpmppm were obtained by treatment with NaCN aqueous solution. Namely, optical resolution of -dpmppm was established through the tetranuclear Pd complexes, which is the first example for methylene-bridged polyphosphines, RP(CHPR)CHPR ( > 0). Furthermore, chiral octapalladium chains, Pd(()-dpmppm)(N≡CCH) ( and ), were synthesized by reacting enantiopure -chiral dpmppm with Pd(CHCN) and [Pd(dba)]·CH and were characterized by spectroscopic and X-ray crystallographic analyses, to determine the absolute configurational structures. The Pd chains are the longest enantiopure chiral single-metal-atom chains structurally characterized, thus far, and the electronic structures were examined on the basis of DFT calculations of .