Synthesen, Strukturen und thermische Abbaureaktionen von Tl I ‐, Pb II ‐ und Se II ‐Komplexen mit 2,2‐Dicyanethylen‐1,1‐diselenolat

Preparation, Structures, and Thermal Decomposition Reactions of Complexes Consisting of Tl I , Pb II , and Se II and 2,2‐Dicyanoethylene‐1,1‐diselenolate The 2,2‐dicyanoethylene‐1,1‐diselenolate‐containing compounds (AsPh 4 ) 2 [Tl 2 (Se 2 C=C(CN) 2 ) 2 ], (AsPh 4 ) 2 [Pb(Se 2 C=C‐(CN) 2 ) 2 ], and (NBu 4 ) 2 [Se(Se 2 C=C(CN) 2 ) 2 ] have been prepared and characterized by single‐crystal structure analysis. The molecular structures of the complex anions 1–3 are significantly influenced by the presence of stereochemically active lone pairs. 1 is dimeric with an Se 4 Tl 2 octahedral centre with a Tl–Tl distance of 3.547(4) Å and an average Tl–Se bond length of 3.143(4) Å. In 2 Pb constitutes the centre of a distorted pseudo‐trigonal bipyramid PbSe 4 E [Pb–Se ave = 2.948(3) Å] with one equatorial position obviously occupied by the lonepair E. In 3 the ligands are coordinated to the central Se, which is situated in a centre of symmetry, in an undistorted way giving rise to a Ψ‐octahedral SeSe 4 E 2 geometry [Se–Se ave = 2.617(2) Å]. The compounds (AsPh 4 ) 2 · 1 , (AsPh 4 ) 2 · 2 and (NBu 4 ) 2 · 3 have been decomposed thermally to yield TlSe, PbSe as well as Se. The observed contamination of TlSe and PbSe with As is avoided by using (NBu 4 ) 2 · 1 and (NBu 4 ) 2 · 2 as precursor materials.