The reaction of bis-organomagnesium compounds with benzoin has been used to determine the effect of co-ordinative solvents on these halogen-free organometallic compounds after the test reaction has been re-examined to establish its reliability. Although the reaction of ether-free dimethylmagnesium is sufficiently different from reactions in which ethers of varying basicity are present to show that co-ordination is significant, this co-ordination seems to be relatively unimportant by contrast to organometallic systems containing halogen.