Metal π-complexes of benzene derivatives. Part. 38. Pentaphenyltriphosphane(5) as a chelating η12-ligand. Unusual formation of an interannular –(PPh)3–bridge at bis(benzene)chromium

(l-6):(1′-6′)-η-Pentaphenyltriphosphane(5)]chromium ( 8 ), which is formed from bis(lithio-η⁶-benzene)-chromium and dichlorophenylphosphane, and which is prepared more rationally from bis(chloro-η⁶-benzene)-chromium and K₂P₃Ph₃, is the first sandwich complex featuring an interannular oligophosphane bridge –(PPh)_n-, n ≥ 2; ³¹P{¹H}- and ¹H-NMR spectra suggest that the stereoisomer 8 -meso₁ is formed exclusively and that the –(PPh)₃- link in this triphospha3]chromocyclophane is non-fluxional in the range 193 < T < 348 K.