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

Abstract

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 [H_6−nNi₃₆Co₈C₈(CO)₄₈]ⁿ⁻ (n = 3–6) polyhydrides by means of acid–base reactions. The structure of the [Ni₃₆Co₈C₈(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 [Ni₃₆Co₈C₈(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.