Synthesis of Mononuclear Strontium Complexes with Polyether and β-Diketonato Ligands

Abstract

Strontium β-diketonate complexes were synthesized by the substitution reaction of the bis(trimethylsilyl) amide of Sr(btsa) 2 •2DME with an ethereal group and β-diketonate ligands. The compounds [Sr(tmge)(btsa)] 2 (1), [Sr(tod)(btsa)] 2 (2), Sr(tmgeH)(tfac) 2 (3), Sr(tmgeH)(acac) 2 (4), Sr(tmgeH)(tmhd) 2 (5), Sr(todH)(tfac) 2 (6), Sr(todH)(acac) 2 (7), Sr(todH)(tmhd) 2 (8), Sr(todH)(hfac) 2 (9), Sr(dmts)(hfac) 2 ( 10), [Sr(mee)-(tmhd) 2 ] 2 (11), and Sr(dts)(hfac) 2 •DME (12) were obtained and analyzed by various techniques, including FT-IR, NMR, TGA (thermogravimetric analyses), and elemental analysis. Complexes 1, 3, 8, 9, 10, 11, and 12 were further structurally confirmed by single-crystal X-ray crystallography, where complexes 1 and 11 showed dimeric structures with μ 2 -O bonds of ethereal groups or tmhd ligands, and complexes 3, 8, 9, 10, and 12 displayed monomeric structures. Interestingly, compounds 10 and 12, which preceded trimethylsilylation of the coordinating ethereal alcohols such as tmhgeH and meeH in the presence of HMDS as byproducts due to highly increasing acidity of them, originated from electron-withdrawing two hfac ligands.

Silylation-Driven Volatility Enhancement in Mononuclear Calcium, Magnesium, and Barium Complexes with Monomethyl or Silyl Ether and Bis(diketonate)

“…During these processes, the deprotonated alcohol moiety in complexes 4a and 4b has the potential to react with HMDS via the S N 2 reaction pathway. However, a previous study using X-ray structural analysis showed that this moiety does not react with HMDS . After the formation of complex 4c , it was hypothesized that the reaction would proceed via a stepwise pathway.…”

“…However, a previous study using X-ray structural analysis showed that this moiety does not react with HMDS. 32 After the formation of complex 4c , it was hypothesized that the reaction would proceed via a stepwise pathway. However, the energy difference between HMDS and complex 4c of the acid–base reaction was large owing to the nonpolar solvent condition (Δ G = 66.62 kcal/mol).…”

“…A previous study observed the tendency of the strontium molecular structure using ethereal ligands with a varying number of oxygen atoms and varying β-diketonate ligands, such as tmhd, acac, tfac, and hfac. When hfacH was used, the hydroxyl hydrogen atom of the ethereal ligand with three or four oxygen atoms was substituted by trimethylsilyl from HMDS and showed high volatility . In this study, ethereal ligands and hfacH were applied to observe alcohol silylation and to synthesize volatile complexes of other two group metals, such as magnesium, calcium, and barium.…”

“…When hfacH was used, the hydroxyl hydrogen atom of the ethereal ligand with three or four oxygen atoms was substituted by trimethylsilyl from HMDS and showed high volatility. 32 In this study, ethereal ligands and hfacH were applied to observe alcohol silylation and to synthesize volatile complexes of other two group metals, such as magnesium, calcium, and barium. Mg(dts)(hfac) 2 ( 1 ), Ca(dts)(hfac) 2 ( 2 ), Mg(dmts)(hfac) 2 ( 3 ), Ca(dmts)(hfac) 2 ( 4 ), and Ba(dmts)(hfac) 2 ( 5 ) were synthesized by controlled substitution reactions using metal bis(bis(trimethylsilyl amide).…”