Synthesis, Structure, and Properties of 9-Phospha-10-silatriptycenes and their Derivatives

Abstract

A variety of 9-phospha-10-silatriptycenes (PSiT) and some derivatives, such as the phosphine selenides and cis-platinum complexes, have been prepared in order to study their structures and characteristics as a phosphine ligand. The 1J(P−Se) NMR coupling constant of the phosphine selenides demonstrate the large s character of the lone pair orbital on the phosphorus atom, attributable to the small C−P−C bond angles of the PSiT framework, as confirmed by X-ray crystallography. The strong trans influence of PSiT has been determined from the 1J(Pt−C) coupling constant measurements of the cis-[PtMe2(psit)2], which is due to the increase in the P−Pt−P angle in the complexes derived from the steric repulsion between the two bulky PSiT ligands. Both the substituent on the silicon and the bridging benzene rings affect the electronic character. Electron-withdrawing substituents on the silicon atom slightly increase the s character of the phosphorus lone pair orbital, and the isopropoxy groups on the bridging benzene rings increase the trans influence.