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[Os18HgxC2(CO)42](x= 2 or 3) with sodium diphenylketyl in tetrahydrofuran a hexaanionic cluster, [Os18HgxC2(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.