With the Mendeley desktop installed you will find that an attempt to install the citation plugin for OpenOffice on your copy of LibreOffice will fail through the usual route of Tools>Install OpenOffice plugin. The prompted “manual” install alternative does not work either.
The way to get this to work in LibreOffice is to open the appropriate Mendeley supplied *.oxt (plugin file) with Libreoffice.
On Mac this would be right click Mendeley Desktop in Applications>Show package contents>Contents>Resources>OpenOfficePlugin> Mendeley*.oxt file. Right click>open with>LibreOffice.
Basically its a manual install of the plugin .oxt file by LibreOffice. Too easy.
Thanks to tkeitt ‘s post on http://feedback.mendeley.com/forums/4941-mendeley-feedback/suggestions/1226271-plugin-for-libre-office