Solvation of alkyllithium compounds. Steric effects on heats of interaction of bases with hexameric versus tetrameric alkyllithiums

摘要: Abstract Heats of interaction Lewis bases with hexameric and tetrameric alkyllithiums in hydrocarbon solution at 25° have been determined by high dilution calorimetry low base to lithium atom ratios. The utilized include tetrahydrothiophene, tetrahydrofuran, triethylphosphine, triethylamine, diethyl ether. organolithiums investigated were n -butyllithium, ethyllithium, isopropyllithium, trimethylsilylmethyllithium, t -butyllithium. basicity order based on initial enthalpies is independent the alkyllithium compound. Larger observed for versus exception -butyllithium which does not interact significantly these bases. sensitivities steric requirements probed comparison 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran. Base coordination more sensitive tetrahydrofuran than trimethylsilylmethyllithium or isopropyllithium. These results are interpreted terms intact aggregate -butyllithium; however, it concluded that corresponding leads directly base-solvated tetramers.