Complex sentence: Other oligomers are known, for instance the lithium salt of 2,2,6,6-tetramethylpiperidine has been crystalised as a tetramer, while the lithium salt of di-(1-phenylethyl) amine crystalises as a trimer.
Split into simpler sentences: Other oligomers are known, for instance the lithium salt of 2,2,6,6-tetramethylpiperidine has been crystalised as a tetramer. While the lithium salt of di-(1-phenylethyl) amine crystalises as a trimer.