Investigations into the preparation of sila-β-diketones via 2-trimethylsilyl-1,3-dithianes: structural characterization of a second polymorph of bis(2,2,6,6-tetramethyl-2-sila-3,5-heptanedionato)copper(II)

The sila-β-diketone, 2,2,6,6-tetramethyl-2-silaheptane-3,5-dione (tmshdH), was obtained in modest yield by the condensation of the lithium cuprate anion of 2-trimethylsilyl-1,3-dithiane anion with 1-bromo-3,3-dimethylbutan-2-one, followed by deprotection of the latent carbonyl moiety. A second polymorph of Cu(tmshd)2 was structurally characterized by X-ray diffraction techniques. Extension of this methodology to the synthesis of disilylated β-diketones was not successful; however, the solid-state structures of the bis-(1,3-dithianyl) precursors were determined, the torsion and bond angles of which evinced unusual steric and stereoelectronic effects.