Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). »Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides«. Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (15. december 2003). »Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation«. Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
Chen, Xin; in sod. (13. december 2019). »Lanthanides with Unusually Low Oxidation States in the PrB3– and PrB4– Boride Clusters«. Inorganic Chemistry. 58 (1): 411–418. doi:10.1021/acs.inorgchem.8b02572. PMID30543295.
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Chen, Xin; in sod. (13. december 2019). »Lanthanides with Unusually Low Oxidation States in the PrB3– and PrB4– Boride Clusters«. Inorganic Chemistry. 58 (1): 411–418. doi:10.1021/acs.inorgchem.8b02572. PMID30543295.
