4 – Magnesium, Calcium, Strontium and Barium

MgBr2·OEt2 (1), which is commercially available and has been examined by different methods in the past, was obtained in crystalline form as a by-product of the reaction of amine-stabilised AlCl solution with mesitylene magnesium bromide. The following unexpected structure was obtained by X-ray techniques: five-coordinate magnesium centres form trigonal bipyramids, which are connected by two common bromine atoms into chains. Structural details and especially the relationship with solid MgBr2, MgBr2·(OEt2)2 and MgI2·(OEt2)2 (2) are discussed in order to illuminate the unusual bonding in 1.

An unexpected structural principle for crystalline mgbr2.oet2 : chains of trigonal bipyramids

Temperature dependence of NQR frequencies in CuBr2 and MgBr2·2Et2O

Magnesium: Annual survey covering the year 1977

Bromine nuclear quadrupole resonance signals corresponding to both isotopes 79Br and 81Br have been observed, at 77 °K, in some crystallized organomagnesium bromides of formula RMgBr•nR′2O, and in MgBr2•nEt2O The low value of the resonance frequencies, of about 33 MHz-to be compared to 220 MHz for a typical bond, bond, shows the ionic character of the Mg—Br bond The fact that the resonance frequencies are found within a restricted frequency range, between 30 and 42 MHz, shows that the Mg—Br bond is only slightly affected by the nature of the radicals R and R′ through the series studied; However the variation of the bromine resonance frequency in this series may be interpreted in terms of the nature of R and R′

Jacky Kress

Papers

Résonance quadripolaire nucléaire du brome dans des composés organomagnésiens