A quartet of articles has recently appeared on the topic of cyclobutadiene.[cite]10.1002/chem.201102942[/cite],[cite]10.1002/chem.201103017[/cite],[cite]10.1002/chem.201203234[/cite],[cite]10.1002/chem.201203235[/cite]. You will find a great deal discussed there, but I can boil it down to this essence. Do the following coordinates (obtained from a (disordered) previously published[cite]10.1126/science.1188002[/cite] x-ray refinement) correspond to a van der Waals complex of 1,3-dimethyl cyclobutadiene and carbon dioxide, or do they instead represent a covalent interaction between these two components resulting in a compound with the chemical name 2-oxabicyclo[2.2.0]hex-5-en-3-one (i.e. not a cyclobutadiene)?