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

Magnesium, calcium, and barium heteroleptic complexes
were synthesized
by the substitution reaction of the bis(trimethylsilyl)amide of Mg(btsa)2·DME, Ca(btsa)2·DME, and Ba(btsa)2·2DME with an ethereal group and hfac ligands (btsa =
bis(trimethylsilyl)amide, DME = dimethoxyethane). The compounds 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 fabricated and analyzed using various techniques, including
Fourier transform infrared spectroscopy, nuclear magnetic resonance
spectroscopy, thermogravimetric analyses, and elemental analysis (dts
= 2,2-dimethyl-3,6,9-trioxa-2-siladecane, dmts = 2,2-dimethyl-3,6,9,12-tetraoxa-2-silatridecane,
hfac = hexafluoroacetylacetonate). The structures of complexes 2, 4, and 5 were confirmed using single-crystal
X-ray crystallography; all complexes display monomeric structures.
All compounds underwent trimethylsilylation of the coordinating ethereal
alcohols (meeH and tmgeH) in the presence of HMDS as byproducts because
of their increasing acidity originating from the electron-withdrawing
hfac ligands. (meeH = 2-(2-methoxyethoxy)ethan-1-ol, tmgeH = tri(ethylene
glycol) monoethyl ether, HMDS = hexamethyldisilazane).