Low-valent main group compounds have interesting structures and reactivities. They can, e.g., feature multiple bonded main group elements. While there are quite a few examples of low-valent tin compounds, stannylidyne complexes (i.e., those with only one substituent at the tin atom) and metallostannylenes are rare so far.

Philip P. Power, University of California, Davis, USA, Robert Wolf, University of Regensburg, Germany, and colleagues have synthesized a rare cyclic cobalt−tin cluster with strong metal–metal bonds. The team reacted [K(THF)_0.2][Co(1,5-cod)₂] with [ArSn(μ-Cl)]₂. (THF = tetrahydrofuran, cod = 1,5-cyclooctadiene, Ar = C₆H₃-2,6{C₆H₃-2,6-ⁱPr₂}₂) in toluene to give the cluster [ArSnCo]₂ (pictured) in yields up to 42 %.

The cluster was characterized using X-ray crystallography and studied using density functional theory (DFT) calculations.  It has a Co₂Sn₂ core with strong bonds between tin and cobalt and a weak tin−tin interaction. The cluster reacts with white phosphorus in toluene to give the ternary cluster [Ar₂Sn₂Co₂P₄], which demonstrates the interesting reactivity of this type of compound. According to the researchers, the developed synthetic strategy could also be used to access other heterobimetallic clusters.

• Synthesis of a Cyclic Co₂Sn₂ Cluster Using a Co^– Synthon,
  Christian M. Hoidn, Christian Rödl, Madison L. McCrea-Hendrick, Theresa Block, Rainer Pöttgen, Andreas W. Ehlers, Philip P. Power, Robert Wolf,
  J. Am. Chem. Soc. 2018.
  https://doi.org/10.1021/jacs.8b08517