Abstract
Sodium, potassium, and calcium compounds of trimethyl((2,3,4,5-tetramethylcyclopentadien-1-yl)ethynyl)silane (CpMe4(C≡CSiMe3)) were synthesized and characterized by X-ray diffraction and standard analytical methods. The sodium derivative was obtained by deprotonation of CpMe4(C≡CSiMe3)H with Na{N(SiMe3)2} to give a monomeric complex [NaCpMe4(C≡CSiMe3)(THF)3]. In a similar reaction, starting from K{N(SiMe3)2} the corresponding potassium compound [KCpMe4(C≡CSiMe3)(THF)2]n, which forms a polymeric super sandwich structure in the solid state, was obtained. Subsequently, salt metathesis reactions were conducted in order to investigate the versatility of the CpMe4(C≡CSiMe3)− ligand in alkaline earth chemistry. The reaction of [KCpMe4(C≡CSiMe3)(THF)2]n with CaI2 afforded the dimeric complex [CaCpMe4(C≡CSiMe3)I(THF)2]2, in which both CpMe4(C≡CSiMe3)Ca units are bridged by iodide in a μ2 fashion. In-depth NMR investigation indicates that [CaCpMe4(C≡CSiMe3)I(THF)2]2 is in a Schlenk equilibrium with [{CpMe4(C≡CSiMe3)}2Ca(THF)x] and CaI2(THF)2, as is already known for [CaCp*I(THF)2].
Highlights
Cyclopentadienyl salts of the alkali metals are probably one of the most versatile reagents in organometallic chemistry
We showed that sodium and potassium cyclopentadienyl is most conveniently prepared in a one-pot synthesis directly from alkali metals with neat dicyclopentadiene at elevated temperature [7,8]
CpMe4(C≡CSiMe3)H was prepared in a modified procedure published by Pudelski et al [23]
Summary
Cyclopentadienyl salts of the alkali metals are probably one of the most versatile reagents in organometallic chemistry. They have been used for the synthesis of countless cyclopentadienyl complexes. Potassium cyclopentadienyl (KCp) was first reported by J. Thiele, who reacted potassium and cyclopentadiene in benzene [1], while the analogous sodium cyclopentadienyl (NaCp) was discovered approximately 50 years later by the groups of E. O. Fischer [2,3] and K.
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