New Trans-Configured Acetylide–Cyanide Platinum(II) Anions: Spectroscopic and Optical Studies

A novel series of phosphorescent stable mixed acetylide–cyanide anionic (NBu₄)₂[trans-Pt­(CCR)₂(CN)₂] (R = Tol (1), C₆H₄CF₃-4 (2), C₅H₄N-4 (3), Np (4)) complexes were prepared by reactions of the neutral [trans-Pt­(CCR)₂(PPh₃)₂] precursors with excess (NBu₄)­CN. The formation of 1–4 takes place through monoanionic [trans-Pt­(CCR)₂(CN)­(PPh₃)]⁻ intermediate species, as confirmed by the isolation of the naphthyl derivative (NBu₄)­[trans-Pt­(CCNp)₂(CN)­(PPh₃)] (5). Further substitution of PPh₃ in 5 by CN^tBu gives (NBu₄)­[trans-Pt­(CCNp)₂(CN)­(CN^tBu)], containing three different isoelectronic ligands. The complexes have been characterized (¹H, ¹³C, ¹⁹⁵Pt NMR, IR, MALDI-TOF), including X-ray crystallography for 2, 4, and 6, and their spectroscopic and optical properties compared to those of the related homoleptic [Pt­(CCR)₄]^2– complexes. Time-dependent density functional theory (TD-DFT) calculations were performed for anions 1^2– and 4^2– and three different conformers of 6^– to provide further insight into the nature of the electronic transitions.