Removing a second mercury atom from [Os18Hg3C2(CO)42]2–: synthesis of [Os18HgC2(CO)42]4– and crystal structure of [PPh3H]3[Os18HgHC2(CO)42]

Abstract

Upon reduction of [N(PPh₃)₂]₂[Os₁₈Hg_xC₂(CO)₄₂](x= 2 or 3) with sodium diphenylketyl in tetrahydrofuran a hexaanionic cluster, [Os₁₈Hg_xC₂(CO)₄₂]^6–, is generated which could only be partially characterised by IR spectroscopy as well as through its chemical reactivity. After chromatographic work-up the tetraanionic cluster [Os₁₈HgC₂(CO)₄₂]^4– was isolated as the exclusive reaction product. This was also obtained in low yield (20–30%) by thermolytic degradation of [Os₁₈Hg₂C₂(CO)₄₂]^2– in CH₂Cl₂. As a consequence of traces of HCl in the CH₂Cl₂ as well as degradation of the cation, the salt [PPh₃H]₃[Os₁₈Hg₂HC₂(CO)₄₂] crystallised from the reaction mixture. An X-ray single-crystal analysis of the latter has established its solid-state structure in which two Os₉C units are µ₆-linked by a central mercury atom. The [Os₁₈HgC₂(CO)₄₂]^4– cluster may be converted into the dimercury cluster dianion [Os₁₈Hg₂C₂(CO)₄₂]^2– by reaction with Hg(O₃SCF₃)₂.