Self‐Alignment of Low‐Valent Octanuclear Palladium Atoms

A linear tetraphosphine, meso‐bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm) was used to synthesize linear octapalladium‐extended metal atom chains as discrete molecules of [Pd 8 (μ‐dpmppm) 4 ](BF 4 ) 4 ( 1 ) and [Pd 8 (μ‐dpmppm) 4 L 2 ](BF 4 ) 4 (L=2,6‐xylyl isocyanide (XylNC; 2 ), acetonitrile ( 3 ), and N,N‐dimethylformamide (dmf; 4 )), which are stable in the solution states and show interesting temperature‐dependent photochemical properties in the near IR region. Variable temperature NMR studies demonstrated that at higher temperature T≈140 °C the Pd 8 chains were dissociated into Pd 4 fragments, which were thermodynamically self‐aligned to restore the Pd 8 chains at lower temperature T<60 °C. The coldspray ionization mass spectra suggested a possibility for further aggregation of the linear tetrapalladium units.