Cs₃UP₂S₈, a coordination polymer containing the unprecedented [U=S]²⁺ sulfidouranium(2+) moiety

Although terminal chalcogeno ligands are well known for the group 5 and 6 transition metals, they are highly unusual for the oxophilic group 4 metals and unknown so far for the lanthanides or actinides. Cs₃UP₂S₈, is the first actinide compound containing a terminal M=S group. It was synthesized by reacting uranium metal, Cs₂S, S, and P₂S₅ in a 4:1:8:3 ratio at 700 C in an eutectic LiCl/CsCl mixture. The crystal structure was determined by single-crystal X-ray diffraction techniques. Cs₃UP₂S₈ crystallizes in the rhombohedral space group R anti 3 [a = 15.5217(8) Aa; c = 35.132(2) Aa, V = 8305.0(8) Aa³, Z = 18]. The crystal structure is based on a tetrahedral network type, wherein the uranium atoms are coordinated by a unusual sulfido moiety and thiophosphate groups in a pseudo-tetrahedral fashion. The U=S distance of 2.635(3) Aa observed in the sulfide moiety is approx. 0.2 Aa shorter than the average U-S single bond length, indicating a double-bond type character. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)