Chiral Self‐Recognition between Stereogenic Tetrapalladium Units Affording Pd 8 Chains Supported by Homochiral Tetraphosphines

By using a chiral tetraphosphine, rac ‐bis[(diphenylphosphinomethyl)phenylphosphino]methane ( rac ‐dpmppm), linear octapalladium chains were synthesized as discrete molecules of [Pd 8 (μ‐ rac ‐dpmppm) 4 L 2 ](BF 4 ) 4 (L=CH 3 CN, dmf, XylNC), [Pd 8 (μ‐ rac ‐dpmppm) 4 ](BF 4 ) 4 , and [Pd 8 (μ‐ rac ‐dpmppm) 4 (Cl) 2 ](BF 4 ) 2 , which are stable in the solution states and characterized by spectroscopic and crystallographic methods to reveal the octapalladium chains supported by homochiral four tetraphosphines. Variable‐temperature NMR studies for a 1:1 mixture of [Pd 8 (μ‐ rac ‐dpmppm) 4 (dmf) 2 ](BF 4 ) 4 and [Pd 8 (μ‐ meso ‐dpmppm) 4 (dmf) 2 ]‐(BF 4 ) 4 in [D 7 ]DMF revealed that the Pd 8 chains were dissociated at higher temperature ( T ≈140 °C) into the Pd 4 units of {Pd 4 (μ‐ rac ‐dpmppm) 2 } 2+ and {Pd 4 (μ‐ meso ‐dpmppm) 2 } 2+ , and they were thermodynamically self‐aligned to restore the Pd 8 chains at lower temperature ( T <60 °C), through perfect chiral self‐recognition between the stereogenic tetrapalladium units.