Reductive C-O Cleavage of Ethereal Solvents and 18-Crown-6 in Ln(NR)/KC Reactions (R = SiMe).

The high reactivity accessible from the reduction of the tris(amide) complexes Ln(NR) (R = SiMe) with potassium graphite in the presence of a variety of ethers is demonstrated by crystal structures of six different types of products of C-O bond cleavage reactions with Ln = Y, Ho, Er, and Lu. Specifically, 1,2-dimethoxyethane (DME) can be cleaved in Ln(NR)/KC reactions as shown by three different types of crystals: [K (crypt)][(RN)Y(OCHCHOCH)], , [(RN)Y(μ-OCHCHOCH-κO,κO')], , and [K(18-c-6)]{[(RN)Lu][(μ-OCHCHO)]}, (18-c-6 = 18-crown-6; crypt = 2.2.2-cryptand). THF can be ring opened by the Y(NR)/KC reaction system, as shown by crystals of the butoxide, [K(crypt)][(RN)Y(OCHCHCHCH)], . The cyclic ether, oxetane, OCH, ring opens in Ln(NR)/KC reactions to form crystals of the propoxide, [K(18-c-6)(OCH)][(RN)Ln(OCHCHCH)], , for Ln = Ho and Er. In EtO, the Y(NR)/KC reactions do not attack the solvent, but C-O cleavage of 18-c-6 is observed to form {[(RN)]Y[μ-η:-O(CHO)K]}, . These Ln(NR)/KC C-O cleavage reactions are typically accompanied by C-H bond activation reactions, which form cyclometalates such as [K(crypt)]{(RN)Ln[N(SiMe)(SiMeCH)-κC,κN]}, (Ln = Y, Ho, Er), and [K(18-c-6)]{(RN)Y[N(SiMe)(SiMeCH)-κC,κN]}, , which are common decomposition products of Ln(NR) reactions. In addition, in this study, the hydride complex, [K(18-c-6)][(RN)YH], , was isolated. NMR analysis indicates that the yttrium reactions form mixtures that consistently contain the yttrium cyclometalates and as major components. These results show the diversity of available reaction pathways for the Ln(NR)/KC system and highlight the inherent difficulties in isolating Ln(II) complexes containing the [Ln(NR)] anion.