Stereoisomers of compounds named tribromocyclobutane Here is the link to the page in which I don't understand the answer to the last question (Question 13). The question states:


  Draw all of the constitutional isomers and stereoisomers of compounds named
  tribromocyclobutane (all structures must contain a cyclobutane ring).


The following image exists as a part of the answer.



But why is the following image not part of the answer? 



Are the above two images not diastereomers (hence stereoisomers)?
The second configuration shown cannot exist simply because of the geometry of the orbitals at the carbon center. The angle between the bromine's (those on the same carbon) is much less than 108° even though there is no forced strain.