Abstract
The new ligand 2-(pyren-1-ylidene)-4,5-bis- (diphenylphosphino)-4-cyclopenten-1,3-dione (pbpcd) has been synthesized from the Knoevenagel condensation using 1-pyrenecarboxaldehyde with 4,5-bis(diphenylphosphino)- 4-cyclopenten-1,3-dione (bpcd). Displacement of the cod ligand in PtCl2(cod) by pbpcd furnishes PtCl2 (pbpcd) (2) in near quantitative yield. Treatment of 2 with the dipotassium salt of toluene-3,4-dithiol (K2tdt) affords the dithiolate compound Pt(tdt)(pbpcd) (3) as a 1:1 mixture of diastereomers. An alternative synthesis of 3 from Pt(tdt)(bpcd) (5) and 1-pyrenecarboxaldehyde also affords 3 in 23% yield. The pbpcd ligand and all new diphosphinesubstituted compounds have been isolated and fully characterized in solution by IR and NMR spectroscopies, and the solid-state structures of 2_CH2Cl2, 3_toluene, and 5_CH2Cl2 established by X-ray diffraction analyses. The solid-state structure of each product exhibits a square-planar architecture at the metal center. The redox properties of the pbpcd ligand and the tdt-substituted compound 3 have been explored by cyclic and differential-pulse voltammetry, and these data are discussed with respect to extended Huckel MO calculations and the nature of the HOMO and LUMO levels in each compound.
