Synthesis of [Tl 4Se 16] 4−: a novel tetranuclear Tl 3+ polyselenide

Abstract

(Ph 4P) 4[Tl 4Se 16] was prepared hydrothermally in a sealed pyrex tube by the reaction of TlCl, K 2Se 4 and Ph 4PCl in a 1:1:1 molar ratio at 110 °C for one day. The red crystals were obtained in 50% yield. Crystals of (Ph 4P) 4[Tl 4Se 16]: triclinic P 1 (No. 2), Z=1, a=12.054(9), b=19.450(10), c=11.799(6) Å, α=104.63(4), β=98.86(6), γ=101.99(6)° and V=2555(3) Å 3 at 23 °C, 2θ max=40.0°, μ=120.7 cm −1, D calc=2.23. The structure was solved by direct methods. Number of data collected: 5206. Number of unique data having F o 2>3σ( F o 2): 1723. Final R=0.075 and R w=0.089. [Tl 4Se 16] 4− consists of four, almost already linearly arranged, tetrahedral thallium centers which are coordinated by two chelating Se 4 2−, two bridging Se 2 2− and four bridging Se 2− ligands. [Tl 4Se 16] 4− sits on an inversion center and possesses a central {Tl 2Se 2} 2+ planar core. The Tl(1)–Tl(1)′ distance in this core is 3.583(6) Å. These two thallium atoms are then each linked to two cyclic Tl(Se 4) fragments via bridging Se 2 2− and Se 2− ligands forming Tl 2Se(Se 2) five-membered rings.