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 CNtBu gives (NBu4)­[trans-Pt­(CCNp)2(CN)­(CNtBu)],
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 12– and 42– and three different conformers of 6– to provide further insight into the nature
of the electronic transitions.