The organometallic chemistry of the alkaline-earth metals. Part 3. Preparation and properties of alkylhalogenometal compounds and related species of calcium, strontium, and barium

Alkyliodo-strontium and -barium compounds can be prepared in tetrahydrofuran (thf) solution at -78 °C in good yields, and solids of composition [MR(I)]·nthf (R = Me, Et, Prⁿ, or Buⁿ, M = Sr, n = 2 or 3; R = Et, M = Ba, n = 1) may be isolated. Characterisation of these products by analysis and other studies is reported. Co-condensation of alkyl halides with Ca, Sr, or Ba metal vapour at low temperature in vacuo gives products which contain solvent-free alkylhalogenometal species (10-25%) which are also investigated. Dicyclopentadienyl compounds, [M(cp)₂] (M = Ca, Sr, or Ba), and di-indenyl compounds, [M(C₉H₇)₂] (M = Sr or Ba), are prepared in high yield by co-condensation reactions. Reactions between various unsaturated organic molecules and iodo(methyl) -strontium and -barium compounds are reported and, except from Ph₂CO, low yields of alkyl addition products are formed. The thermal decomposition of (ethyl)iodostrontium species produces a variety of hydrocarbon and other products, and studies on this system at 18 °C indicate the occurrence of some saturated C-C bond-cleavage reactions under mild conditions.