INSERTION REACTIONS OF SMALL MOLECULES INTO GROUP-2 METAL ALKOXIDES -STRUCTURAL CHARACTERIZATION OF CO3)(O2COME)(8)(MU(3)-OME)(8)(MEOH)(13)].MEOH.C7H8

The SO2 inserted compounds [M(O2SOMe)(2)(MeOH)(2)](infinity) (M = Mg 1 ; M = Ca 2) were synthesized from the reaction of the corresponding [M (OMe)(2)](infinity) complexes in methanol, followed by recrystallizati on from either n-hexane or toluene. The reaction of COS or CS2 gas wit h [M(OMe)(2)](infinity) in methanol, yielded the inserted products [M( {OCS}OMe)(2)(MeOH)(x)](n) (x = 2, M = Mg 3; x = 3, n = 2, M = Ca 4) an d [M(S2COMe)(2) (MeOH)(x)](n), (x=6, M=Mg 5; x=4, M=Ca 6), respectivel y. The analogous reaction of[M(OMe)(2)](infinity) (M=Mg, Ca) with CO2 gas gave the mixed methoxide/methylcarbonato compounds [Mg(O-2 COMe)(O Me)(MeOH)(1.5)](n) 7a and [Ca(O2COMe)(OMe)(MeOH)](n), 8. Recrystalliza tion of 7a from a ''wet'' hydrocarbon solvent mixture led to the cryst alline product [Mg-9(CO3)(O2COMe)(8)(OMe)(8) (MeOH)(13)].MeOH.C7H8 7b. The corresponding insertion reaction of CO2 gas with [M(OEt)(2)](infi nity,) (M = Mg, Ca) gave the mixed ethoxide/ethylcarbonato compounds [ M(O2COEt)(OEt)(EtoH)(2)](n) (M = Mg 9, M = Ca 10). Similarly, the reac tion of CO2 gas with [Mg(OR)(2)](infinity) (R = Pr-i, Bu-t) in the par ent alcohol. resulted in the [Mg(O2COR)(OR)(ROH)](n), compounds (R = P r-i 11; R = Bu-t 12). All compounds have been characterized by spectro scopic techniques including NMR (H-1 and C-13) and IR spectroscopy, an d in selected cases by TGA/DSC. Complex 7b was unambiguously character ized by single crystal X-ray diffraction. It was established that 7b i s a nonameric complex comprising of two Mg4O4 cubes, with a remote nin th magnesium atom held in position via two bridging methylcarbonato gr oups and an unusual mu(5)-carbonate ligand. (C) 1998 Published by Else vier Science Ltd. All rights reserved.