Five-coordinate Pd(ii) orthometallated triarylphosphite complexes

Abstract

The reaction of the orthopalladated triarylphosphite complexes [{Pd(µ-Cl){κ²-P,C-P(OC₆H₂-2,4-R₂)(OC₆H₃-2,4-R₂)}₂] (R = H, ^tBu) with bis(2-diphenylphosphinoethyl)phenylphosphine leads to a five-coordinate palladium(II) (R = H) and a mixture containing four-and five-coordinate species (R = ^tBu). The crystal structure of the five-coordinate species [Pd{κ²-P,C-(P(OC₆H₄)(OC₆H₅)₂}{bis(2-diphenylphosphinoethyl)phenylphosphine}][SbF₆] is presented. This complex reacts with hydrogen peroxide or [AuCl(tht)] to give four-coordinate complexes in which the displaced phosphine residue is either oxidised or coordinated to gold chloride; this demonstrates that the five-coordinate complexes are labile in solution. By contrast, the reactions of the dimeric precursors with 1,1,1-tris(diphenylphosphinomethyl)ethane give four-coordinate complexes in the solid state, although evidence is presented that the smaller phosphite-containing system is five-coordinate at room temperature or higher in solution.