Synthesis and characterization of phosphinimine-substituted trifluoro- or trichloro-p-benzoquinones and their cationic Rh(I) complexes. The crystal and molecular structure of 3,5,6-trichloro-2-(triphenylphosphinimino)-p-benzoquinone

Abstract

Reaction of tetrafluoro- or tetrachloro-p-benzoquinone with silylated phosphoranimines R2R′P=NSiMe3 (R = Ph, Me) yields very highly colored monosubstituted derivatives of the p-quinone that act as two-electron acceptors showing clean, reversible CV traces. The molar absorptivity values are typical of dyes. These ligands also form chelate complexes with Rh(I) precursors using the quinone oxygen and the imine nitrogen donor sites. One of the quinone derivatives, 3,5,6-trichloro-2-(triphenylphosphinimino)-p-benzoquinone, has been structurally characterized. The iminated quinone shows a normal P=N bond length (1.597(2) Å) and P-N-C angle (P-N-C(3) 132.7(2)°). The N—C(3) bond, 1.327(3) Å, is a little shorter as is expected for the establishment of a conjugated structure between the phosphinimine substituent and the quinone ring. Some steric crowding pushes the Cl and N substituents on the quinone ring out of the plane of the ring. Key words: quinones, phosphinimines, fluorine, chlorine, rhodium.