Selective synthesis of the [Ni36Co8C8(CO)48]6- octa-carbide carbonyl cluster by thermal decomposition of the [H2Ni22Co6C6(CO)36]4- hexa-carbide

The thermal decomposition in thf solution of [H2Ni22Co6C6(CO)(36)](4-) results in the new [HNi36Co8C8(CO)(48)](5-) bimetallic Ni-Co octa-carbide, which can be converted into the closely related [H6-nNi36Co8C8(CO)(48)](n-) (n = 3-6) polyhydrides by means of acid-base reactions. The structure of the [HNi36Co8C8(CO)(48)](6-) hexa-anion has been established via X-ray crystallography, showing that the eight interstitial carbide atoms are lodged within different metal cages. Thus, two C-atoms are enclosed within regular square anti-prismatic Ni8C cages, four within irregular Ni8C square anti-prismatic cages, and the last two within mono-capped trigonal prismatic Ni5Co2C cages. The structure of [HNi36Co8C8(CO)(48)](6-) is non-compact and closely related to [Ni32C6(CO)(38)](6-) and [HNi38C6(CO)(44)](5-). [Ni36Co8C8(CO)(48)](6-) approaches the nanosize regime and the whole molecular ion has a diameter (measured from the outer oxygen atoms) of ca. 1.61 nm.