Gold and Silver Chains Supported by Linear Hexaphosphine Ligands

A new linear hexaphosphine, rac‐cis,cis,trans‐ bis{(diphenylphosphinomethyl)phenylphosphinomethyl]phenylphosphino}methane ( P₆ ), was synthesized and isolated as a pure isomer, confirmed by transforming to the corresponding phosphine sulfide. The methylene‐bridged linear hexaphosphine readily organized flexible gold(I) and silver(I) hexanuclear chains, M₆(μ‐ P₆ )₂]X₆ (X₆=(OTf)₆, M=Au ( 1 ), Ag ( 2 ); X₆=Cl₂(PF₆)₄, M=Au ( 3 )). The hexaphosphine also supported a tetrasilver(I) complex Ag₄(μ‐ P₆ )₂](OTf)₄ ( 4 ), which was readily transformed by treatment with AgOTf into 3 , revealing a drastic alternation of the two P₆ arrangement. The hexagold(I) chains exhibited a considerably red‐shifted absorption (～410 nm) and emission (540–580 nm) to ¹5d_σ*→6p_σ] and from ³5d_σ*→6p_σ] excited states of the metal centers, respectively. The new linear hexaphosphine could be a useful tool to construct linear metal clusters as subnano building blocks.