Novel Luminescent Mixed‐Metal PtTl‐Alkynyl‐Based Complexes: The Role of the Alkynyl Substituent in Metallophilic and η 2 (π⋅⋅⋅Tl)‐Bonding Interactions

A novel series of [PtTl 2 (CCR) 4 ] n ( n =2, R=4‐CH 3 C 6 H 4 (Tol) 1 , 1‐naphthyl (Np) 2 ; n =∞, R=4‐CF 3 C 6 H 4 (Tol F ) 3 ) complexes has been synthesized by neutralization reactions between the previously reported [Pt(CCR) 4 ] 2− (R=Tol, Tol F ) or novel (NBu 4 ) 2 [Pt(CCNp) 4 ] platinum precursors and Tl I (TlNO 3 or TlPF 6 ). The crystal structures of [Pt 2 Tl 4 (CCTol) 8 ] ⋅ 4 acetone, 1⋅ 4 acetone, [Pt 2 Tl 4 (CCNp) 8 ] ⋅ 3 acetone ⋅ 1/3 H 2 O, 2⋅ 3 acetone ⋅ 1/3 H 2 O and [{PtTl 2 (CCTol F ) 4 }(acetone)S] ∞ (S=acetone 3 a ; dioxane 3 b ) have been solved by X‐ray diffraction studies. Interestingly, whereas in the tolyl ( 1 ) and naphthyl ( 2 ) derivatives, the thallium centers exhibit a bonding preference for the electron‐rich alkyne entities to yield crystal lattices based on sandwich hexanuclear [Pt 2 Tl 4 (CCR) 8 ] clusters (with additional Tl⋅⋅⋅acetone ( 1 ) or Tl⋅⋅⋅naphthyl ( 2 ) secondary interactions), in the C 6 H 4 CF 3 (Tol F ) derivatives 3 a and 3 b the basic Pt II center forms two unsupported PtTl bonds. As a consequence 3 a and 3 b form an extended columnar structure based on trimetallic slipped PtTl 2 (CCTol F ) 4 units that are connected through secondary Tl⋅⋅⋅(η 2 ‐acetylenic) interactions. The luminescent properties of these complexes, which in solution (blue; CH 2 Cl 2 1 , 2 ; acetone 3 ) are very different to those in solid state (orange), have been studied. Curiously, solid‐state emission from 1 is dependent on the presence of acetone (green) and its crystallinity. On the other hand, while a powder sample of 3 is pale yellow and displays blue (457 nm) and orange (611 nm) emissions, the corresponding pellets (KBr, solid) of 3 , or the fine powder obtained by grinding, are orange and only exhibit a very intense orange emission (590 nm).