摘要
Rare-earth metal boroxides are not only rare and of great synthetic challenge but also important theoretically due to their unrevealed bonding characteristics.In this paper,we report the synthesis,characterization,and bonding characteristics of the 4f-block metal boroxide complexes ^(Mes)DAD_(2)LuOB(C_(6)F_(5))X(4-Lu,X=C_(6)F_(5);5-Lu,X=NC_(13)H_(10))with two chelating radical-anionic 1,4-diazabutadiene(DAD)ligands.The synthesis of 4-Lu or 5-Lu involved three steps,during which the radical-anionic DAD ligands could be kept stable:(1)the reaction of LuCl_(3),^(Mes)DAD,and potassium graphite(KC8)afforded the diradical rare-earth metal chloride ^(Mes)DAD_(2)LuCl·tetrahydrofuran(THF)(1-Lu);(2)the salt metathesis of 1-Lu with two alkali metal amides gave lutetium bis(diazabutadiene)amides 2-Lu or 3-Lu,respectively;and(3)2-Lu or 3-Lu reacted with B(C_(6)F_(5))_(3)·H_(2)O,resulting in the formation of rare-earth metal boroxides 4-Lu or 5-Lu.The radical-anionic nature of DAD ligands in these complexes were proven by their bond lengths and coordination modes in single-crystal structures.DFT calculations clearly show the bonding of 4-Lu can be divided into three major types of Lu-O orbital interactions,which can be categorized asσ-donation,π-donation,and d-π-conjugation.The triple Lu-O orbital interactions cooperatively make a Lu-O single bond and contribute to the linear Lu-O-B structure.
基金
supported by the Natural Science Foundation of China(nos.21725201 and 21890721).
