Sterically shielded primary anilides of the alkaline-earth metals of the type (thf)nAe(NH-Ar*)2 (Ae = Mg, Ca, Sr, and Ba; Ar* = bulky aryl)

Abstract

Metalation of 2,4,6-triphenylphenylamine (H₂N-C₆H₂-2,4,6-Ph₃, 1a) and 4-methyl-2,6-bis(diphenylmethyl)aniline (2,6-bis(diphenylmethyl)-p-toluidine, H₂N-C₆H₂-4-Me-2,6-(CHPh₂)₂, 2a) with dibutylmagnesium and Ae[N(SiMe₃)₂]₂ with a stoichiometric 1 : 2 ratio in THF at room temperature yields the corresponding primary anilides [(thf)_nAe{N(H)-C₆H₂-2,4,6-Ph₃}₂] (Ae/n = Mg/2 (1b), Ca/2 (1c), Sr/3 (1d), and Ba/3 (1e)) and [(thf)_nAe{N(H)-C₆H₂-4-Me-2,6-(CHPh₂)₂}₂] (Ae/n = Mg/2 (2b), Ca/3 (2c) and Sr/2 (2d)), respectively. The 1 : 1 reaction of Mg(n/sBu)₂ and MgPh₂ with 2a leads to the formation of heteroleptic [(thf)₂Mg(R){N(H)-C₆H₂-4-Me-2,6-(CHPh₂)₂}] (R = n/sBu (2b_Bu), Ph (2b_Ph)). At 50 °C, the strontium complex 2d liberates one equivalent of 2avia intramolecular deprotonation of the triarylmethyl functionality yielding dinuclear [(thf)₂Sr{N(H)-C₆H₂-4-Me-2-(CPh₂)-6-(CHPh₂)₂}]₂ (2d′). The barium compound is significantly more reactive and regardless of applied stoichiometry the isotypic barium congener [(thf)₂Ba{N(H)-C₆H₂-4-Me-2-(CPh₂)-6-(CHPh₂)₂}]₂ (2e′) forms. The molecular structures of 1c, 2d, 2d′, and 2e′ are stabilized by metal-phenyl π-interactions.