A comment made on the previous post on the topic of hexa-coordinate carbon cited an article entitled “Observation of hypervalent CLi6 by Knudsen-effusion mass spectrometry“[cite]10.1038/355432a0[/cite] by Kudo as a amongst the earliest of evidence that such species can exist (in the gas phase). It was a spectacular vindication of the earlier theoretical prediction[cite]10.1021/ja00379a051[/cite],[cite]10.1021/ja00356a045[/cite] that such 6-coordinate species are stable with respect to dissociation to CLi4 and Li2.