The charge-transfer interaction of 7,7,8,8-tetracyanoquinodimethane with trans-bis(trialkylphosphine)-dialkynylplatinum(II) and related complexes

Abstract

7,7,8,8-Tetracyanoquinodimethane ★★ (TCNQ) showed charge-transfer interaction with trans-bis(trialkylphosphine)dialkynylplatinum(II), trans-[R′ 3P) 2Pt-(CCR) 2], (R′ = Me, Et, Pr, Bu, and R = H, Me, CH 2CH, CH 3CC or Ph), and their palladium(II) and nickel(II) derivatives. The following 1 1 adducts were isolated as stable purple-black crystals: ▪ These adducts showed a characteristic absorption band in the visible region (λ max; 506–555 nm in CH 2Cl 2). From the study of their formation constants and consideration of the molecular geometry of component molecules, it was deduced that electron was donated from the alkynyl groups to TCNQ. This characteristic property of the alkynyl group which coordinates to transition-metal atom is regarded as the consequence of the back-donation of electrons from the central metal which increases the electron density on the alkynyl groups and enhances their donor properties.