On the usability of salt metathesis reactions for the synthesis of sterically crowded tris-formamidinate Ln() complexes: success and limits. Spontaneous reduction of Eu() to Eu()

• Published in: New journal of chemistry Vol. 46; no. 25; pp. 11994 - 121
• Main Authors: Bashirov, Denis A, Kolybalov, Dmitry S, Mironova, Olga A, Sukhikh, Taisiya S, Konchenko, Sergey N
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 27.06.2022
• Subjects: Chemical synthesis; Decomposition reactions; Gadolinium; Metathesis; Reduction; Toluene
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d2nj01589g

Homoleptic [Ln(FormDipp) 3 ] (FormDipp = CH(NDipp) 2 − (Dipp = 2,6-diisopropylphenyl), Ln = Nd, Eu) complexes bearing three bulky formamidinate ligands were successfully obtained using the salt metathesis approach, viz. the reaction of [Ln(FormDipp) 2 Cl(thf) n ] (Ln = Nd ( n = 2), Ln = Eu ( n = 1)) with K(FormDipp) in toluene at 100 °C. This method is not useful for the Ln smaller than Eu: all attempts to realize it for Gd and Tb were unsuccessful. In the case of Eu, the tris-formamidinate complex was obtained in toluene, but in a thf/toluene mixture, a spontaneous reduction of Eu( iii ) to Eu( ii ) leading to the formation of [Eu(FormDipp) 2 (thf) 2 ] was observed. The Eu( iii ) to Eu( ii ) conversion is rather sterically induced. UV-Vis spectroscopy monitoring of the reaction indicates it to be a zero-order process. Possible routes of the reaction are proposed. New homoleptic complexes of Eu 3+ and Nd 3+ bearing three bulky N , N -bis(diisopropylphenyl)formamidinates were prepared using salt metathesis in a toluene medium. In the presence of THF, the sterically-induced reduction of Eu 3+ to Eu 2+ was observed.