A Closer Look at the Synthesis and Characterization of Alkaline Earth Metal Tetraarylborates and Heteroleptic Tetraarylborate Pyrazolates

Compounds containing s-block metals are highly sought after as precursor materials for the Metal Organic Chemical Vapor Deposition (MOCVD) process with applications for novel and improved electronic materials. Previous work in the Ruhlandt Group has been focused on the synthesis and characterization of novel homoleptic alkaline earth (Ae) metal pyrazolate and tetraarylborate complexes, while understanding the importance of secondary interactions such as M- in the isolation of these compounds. More recently, it was further proposed that the pyrazolate and tetraarylborate ligand systems combined with an Ae silyl amide via transamination may very well result in an improved heteroleptic MOCVD potential precursor due to the ligand systems’ capability of extended M- interactions. Herein are described efforts to further understand and successfully reproduce, with significantly improved yields from ~1 – 15% to 50% (ave.), these unprecedented Ae tetraarylborates [Ae(B((3,5-Me2)C6H3)4)2(thf)n (Ae = Ca, 1 † , n = 0; Ae = Sr, 2 † , n = 0; Ae = Ba, 3 † , n = 1) and [Ae(B((4-tBu)C6H3)4)2(thf)n (Ae = Ba, 4 † , n = 0) and heteroleptic tetraarylborate pyrazolates [Ae(thf)2(Et2O)2(tBu2pz)][B((3,5-Me2)C6H3)4] (Ae = Ca, 5 † ) and [Ae(thf)2(tBu2pz)(B((3,5-Me2)C6H3)4)] (Ae = Sr, 6 † ; Ba, 7 † ) that exhibit various ion association modes along with M- interactions. In addition, little is known about the formation of these compounds; as such, there is still a need to examine and further explore the synthesis of various Lewis bases to provide an improved understanding towards the structure-function relationships of these complexes