Unexpected Isomerization of Hexa-tert-butyl-octaphosphane

Abstract

Octaphosphane {cyclo-(P₄ tBu₃ )}₂ (1) undergoes an unexpected isomerization reaction to the constitutional isomer 2,2',2'',2''',3,3'-hexa-tert-butyl-bicyclo[3.3.0]octaphosphane (2) in the presence of Lewis acidic metal salts. The mechanism of this reaction is discussed and elucidated with DFT calculations. The results underline the fascinating similarity between phosphorus-rich and isolobal carbon compounds. The new bicyclic octaphosphane 2 shows a dynamic behavior in solution and reacts with [AuCl(tht)] (tht=tetrahydrothiophene) to give a mono- ([AuCl(2-κP³ )], 3) and a dinuclear complex ([(AuCl)₂ (2-κP³ ,κP^3' )], 4). With cis-[PdCl₂ (cod)] (cod=1,5-cyclooctadiene), the chelate complex ([PdCl₂ (2-κ² P² ,P^2' )], 5) with a different coordination mode of the ligand was obtained.

Keywords: gold; isomerization; oligophosphanes; palladium; phosphorus.