THE STRUCTURE OF 1,4-BISORGANOMAGNESIUM COMPOUNDS IN SOLUTION: 1,4-BIS(BROMOMAGNESIO)BUTANE AND (DIMERIC) MAGNESACYCLOPENTANE

Article abstract of DOI:10.1016/S0022-328X(00)93974-3

1,4-Bis(bromomagnesio)butane (VI) and magnesacyclopentane (IV) were prepared and investigated as such and in combination with MgBr2 by measuring the degree of association in THF solution at three temperatures.It was established that IV does not exist as such, but is completely dimerized to 1,6-dimagnesacyclodecane (V).A Schlenk equilibrium is established between V and VI with K₄(28.17 deg) = 100 +/- 50, K₄(39.75 deg) = 250 +/- 100 and K₄(48.84 deg) = 500 +/- 200 and the thermodynamic parameters ΔH₄ = 15 kcal mol^-1 and ΔS₄ = 59 e.u..These values are veryclose to those of the higher homologue, 1,5-bis(bromomagnesio)pentane (III) and of ethylmagnesium bromide.It is concluded that these di-Grignard reagents behave essentially like the normal monovalent Grignard reagents.